G RI FFIN S S TA N DARD P U B LI G A T I ON S
’
T
B y
H E OV A N I B E P R O C E SS O F G O L D E " T R A C T I O N
T H I R D ENGL I S H E D I T I O N
I n lar g e 8 v o
J A M ES P A R K
.
F u ll y I ll u s t ra ted
C l o th
,
.
.
.
73
.
L A N DS
Th
:
eir
6d
.
.
P
r
o
p
ti
e
A dv t g
N H U G H R O B ER T M I LL B s L L D
F ll y I ll s t ra ted 5
A Pra ti l H db
R O S P E C T I N G FO R M I N E R A L S
P s H ER B ER T c ox
F G S
TH
E mm
I ll t ra ted 5
OO D S U P P L Y
B y R O B E RT B R U C E
W
i th A pp ndi x
F
R D F D b y C A M I T C H E LL M A F I C 4 6 d
EW
R
e
.
,
eo re
.
and
u c s
s
.
,
.
ec
s
.
u
u
,
c
on
I RD
.
.
.
,
.
SE
M
VE
.
.
I N I NG L A W O
J ALFO R D
P R AC T
P
B y
R OF
1 08 6d
.
P
O
.
.
.
.
.
M
N I
.
e ars
.
.
With
.
.
.
N T H ED I T I O N
.
c
F G S
.
G E O LO G Y
.
,
G ER
B E RI N
.
R ev ise d
IC AL
Wi th
.
,
Revi s ed
a ram s
,
By P
.
Di g
P
.
net
.
P
on
RE
.
on
F I FT H
.
PA
L E ON
E ITI
D
108 6d
.
ANAL YSI S A N D
S
ER
M es
.
.
O
N
,
E L E M E N TA R Y
OO K O F
S E" T ON
A
H U M B OL D T
Gs
.
s
.
F C S
,
.
.
T HI RD
.
.
.
.
.
LE
VI L
88 6d
.
.
GER
C B ER I N
.
.
,
.
A SS A Y I N G
.
.
I ll u s t ra ted
an d
.
G REN
R O F.
r of u s e l y
in
B y W A
C ou r s e f o r tu de n ts o f S c h oo l s o f
F C S
F u ll y I ll u s t ra t e d
12
6d
a n d C H A S WA L K
,
-B
5
B y C HA RL ES
e tio n
S
a
,
S E CO N D E DI T I O N
’
T E" T
By
.
.
.
I C A L G E O LO G Y
G RE N V I LL E COL E
U D I ES I N
.
A
s
.
.
.
e
,
B y J J
.
ET A L L U R G
Y
.
I SH EM P I R E
I n C ro wn 8v o C l ot h
83 6 d
,
F C S
.
,
By
.
.
E N -A I R S T
COLE
S S A YI N G
us
.
es
o ok
an
ca
F T H E B R IT
,
I
DS I N
A T OL OG Y
Revi s ed
.
.
,
8
.
.
S
OO
an a
v
.
A
.
M A C LE O D
net
T hre e
A
.
,
B A
.
B Sc
,
.
.
.
,
.
M E T A L L U R GY
B
E D I T I ON Revi s ed I ll u strate
.
.
,
.
G
G
C
O
E TT I N G
J
I ll
.
s ra ti o s
o
o h A ri a
C
.
I D ING
JU L I A N
I u
t
ll s tra io
G OL D
an d
ns
.
.
i
.
SI L
S
.
I ll
Wi th
.
.
B y H
nu m e ro u s
.
M ap s ,
F O R B ES
Pl at e s an d
,
.
M IN IN G
E D I T IO N R e vise d
B y S
.
s t ra t io s
n
and
,
34 s
.
I R
0
E n l arg e d
.
FOS T ER
L E N E VE
b y B EN N ET T H B R O U G H ,
.
E L E M E N T S O F M I N I N G A N D QU A R R Y I N G
FR S
W i th n e arl y 300 I ll u s t rat i o n s
0 L E N E V E F OS T ER D S c
HE
.
,
.
.
,
,
.
.
.
.
.
By
.
7s 6 d
.
.
.
L A S T I N G : A N D T H E U S E O F E " P LO S I V E S
By
G U T T MA N N
S E CO N D E D IT IO N t h o ro u g hl y Revi s ed
Wi th I ll u st ra t i o n s a n d F ol ding P la te s 10 3 6 d
8vo
.
,
,
.
.
L
.
O R ES
VER
,
S T ON E
I" T H
D Sc , F R S
W th 7 1 5 u
F G 8
.
.
A N D
E DG AR S M ART
21 3 n e t
.
RE A N D
.
u
.
.
.
.
A F R I C A B y T H E O KA S S N E R
With C ha p te r on t h e Ag r i c u l t u ral P rosp e c ts of
S OU T H
IN
ll I ll s tra ted
F
.
.
u y
I n
r wn 8 v o
4 3 6d
f c
S ut
.
B
.
.
.
,
O L D S EE Kl N G
SI R
ne t
Ha n dbook fo r Practi c a l M e n
B y
T H I R D E D IT I O N Re vis ed
Wi th P la te s and
old-m in in g
.
.
YAN
G
A
.
C F J OH N S O N ,
n
3s 6 d
u t
.
T
G OL D
O N DON :
C HA R LE S G R I FF I N
8: C O
.
,
L
T D
.
.
,
.
OS CAR
I
n
l a rg e
.
E"
ET
ER
S T R EET , S T R A N D
.
T E" T B OOK DE
A
-
MI N I N G
G E OL OG Y
OF MI N I N G
FO R T H E U S E
A N D M I N ER S
JA M ES
S T U D EN T S
.
I A RK
Z
'
’ R OF HI N I F Q A N D MI N I N G
,
EOL OG Y ;
D I R EO I O B O F OT A G O U N I V ER S I T Y S C HOO L O F M I N E S
M E MB E R OF T H E I N S T I T U T IO N O F M I N I N G A N D M ET A L L U R G Y ;
M E M B E R O F T H E AM ER IC AN I N S T IT U T E O F M I N I N G EN G I N EE R S
FEL L O W OF T H E G EO L OG I CA L S OC I ET Y O F L O N D O N ;
L A T ] P R ES I D ENT OF T H E N EW Z E A L A N D
P B OW
G
‘ ’
I N S T I T U T E OF
m m:
C H A R L ES
m
9 EN G I
N E ER S
.
7 8 s um
ma tions anb 3 p late s
G R I FF I N
E " E TE R
.
CO M P A N Y , L I M I T ED
S T R EE T
1 90 6
,
S T RA ND
.
i
h
t
s
R
e
serve
l
d
A
l
R
g
[
]
.
,
P R E F A CE
.
i s only in rec e nt y e a rs tha t M in i ng G e ology has b e e n r e garded
"
as o f s u ffi c ie n t impo r tanc e to warran t i ts e l e vation to the di g ni ty
of a distinct depa rt ment in t h e M ining Schools a n d Colleg e s of
E nglish speak i ng communi t ies F or long e nough it was t r eate d
as a subord i nat e subj ect b e ing taught for th e most pa rt as
an introduc ti on t o th e principl e s of mining a t a time in h i s
academic car ee r when t he young und e rgradua te posse ssi n g no
pe rsonal e xp e rience of or e bodi e s as t hey oc c u r in N ature was
l e as t abl e to gra sp t h e t ru e b e aring of the s ubj e c t i n i ts
relation to th e economics of th e mining indus t ry
I n th e
mining acad e mi e s of Contin e ntal E urop e e con omic g e ology has
always occupi e d a prom i n e n t and respec te d place
Th e ma t ter i n the follow i ng pag e s compris e s a series of
l e c t ur e s issued i n Bulle t in for m at t h e e nd of 1 90 2 T h e
e xhaus ti on of that li ttl e publicat ion has e ncourag e d t he au thor
to pr e s e n t t h e sam e mat te r i n t h i s revi s ed a n d e nlarg e d form
The n e w chap te rs on O r e s and Mi n e rals Consi de re d E conomi
”
”
—
cally
Mi n e Sampl i ng and O r e Valua t ion and Th e E xamina
ti on and V aluation of Mi n e s hav e b ee n added t o comply w i th the
requir e men t s of th e n e w curr i culum for th e as s ociate d iplomas
in M ining Met allurgy and G eology
Th e g e nes i s of or e d e posits is a subj e ct surr o u nd e d by ma n y
perplexing problems Th e ch ie f diffi c u l ty en c ountered by th e
tea cher is t hat th e g e neral i sat i ons have no t yet been crys tall i sed
in forms s u ffi c ie n tly de fin it e to be un i versally a cc e pted as fi rs t
I
T
'
-
.
,
,
,
-
,
.
,
.
.
.
“
“
-
,
,
-
,
,
.
'
-
.
principles
The publication of th e lat e Professor P ose pn y s classic pap e r
on T he G enesis of O re D ep osi ts in 1888 may b e sai d to
.
’
'
-
vi
P R EFA C E
.
hav e mark e d t he beginning of a new era in the history of
e conomic geology Since that dat e t he lit e ratur e of the subj ect
has been e nriched by the writings of V ogt S t e lzn e r B e ck
de L aunay Van His e Rickard Becker E mmons G r e gory K e mp
Chamberlain L indgren Weed Spurr Sir C L e N eve Foster
S H e rbert Cox G renville Cole and oth e r distinguished g e ologists
The Am e rican School has not e ndorsed th e e xtreme vi e ws of
P os e p n y or the fascinating th e ori e s of S a n db e rg e r but gradually
d e v e lop e d a c onception lying somewher e betw e en th e two with
a d i st i nct leaning towards th e t e achings of th e form e r
With r e spect t o M in e Sampling and Va lu a t ion it is manifest
that no hard and fast rul e s can b e lai d down O i Am e rican
E nglish and G e rman mining e ngin ee rs with whom th e author
has be e n associated i n min e e xam i na ti on i t is noteworthy that
all w e r e agr e ed as t o the prim e ess e n t ials although d i ffe rin g
within ce rtain small limi ts in mat te rs of procedure and routine
D iiTe r e n c e s in minor details must always e xist wh e r e men vary
i n e xp e rience and temperament
Stud e nts r e ading for advanced work a n d honours will fi n d a
f e rtile fi e ld of r e f e r e nce in such e xc e llent works as T h e G enes is
of
Or e D ep oszts publ i sh e d by th e American I ns t i t u t e of M ining
E ngine e rs 5 the treatis e s on O r e D e pos i ts by S te lzn e r Beck
Phill i ps and L ouis T h e S a mp lin g a nd Va lu a tion of M ines
by R i ckard ; t h e spl e nd i d M emo i rs and Repo rts of the G eological
Surv e y of th e Unit e d States ; and t h e valuabl e pap e rs scatt e r e d
thro u gh th e Transact i ons of th e Am e rican I nstitut e of M ining
E ng i n ee rs of th e I ns t itut i on of M in i ng E ng i n ee rs of th e
I ns ti tution of M ining a n d Me tallurgy and of th e N ew Z e aland
I nsti t ute of M ining E ngin ee rs Th e acknowl e dgmen t s of th e
author are due t o th e writers of th e s e pap e rs and to fri e nds
in many places for much valuabl e assistanc e in th e pr e paration
of these pages
T H E AUTH O R
.
,
,
.
,
,
.
,
,
,
,
,
,
,
,
,
,
,
,
.
,
,
,
,
.
‘
,
,
.
,
,
,
.
.
'
-
,
-
,
,
,
,
,
,
,
.
.
.
U
N I V E RS I T Y
,
DU
N ED I N
Al a rch 1 90 6
.
,
N
.
Z
.
,
CO N T E N T S
CHAPT ER
I
.
I N T R O D U CT O RY
T he
.
.
—
G
l
h
i
l
l
t
t
E
ope
P
r
po
e
o
f
eo
og
eo
og
t
r
c
r
e
o
f
r
t
h
d
G
S
S
y
B egi n i ng o f G eo l ogi l T im — T h A tio n o f W ter i D t y i g
C r t m o tly S edi m e t ry — T h
E rth
d R fo rm i ng — T h
Al terati on o f S edim ent rie — F o il C onte t — G eolog i al T i me
fl w
R oc k — O
m arked b y D i ti n ti ve L i fe— O rig in o f I gne
—
—
—
P
l
o
k
D
ke
o
k
l
to
n
i
B
o
e
A
te
r
t
i
o
n
o
f
I
g
eo
n
R
R
y
—
o
k
d M i neral i I gn eo
Ro k — T h I fl
of
M etal
R
D y k — Cl ifi ti o f I gneo
R o k —I m po rtan e
f Petro
an
c
n
an
e
-
’
a
s
c
s
es
c
C HAPT ER
C LAS S I F I CAT I ON
c
ver
s
o
c
us
s
II
n
e
s
u e nc e
o
c
.
M I N E R A L D E P OS IT S
OF
e
a
us
us
on
ca
ss s
n
s
n
n a
n s
c
a
e s ro
s
ss
u
s
an
a ss
n
ou s
c
s
e
a
c
s
u
c
us
s
s
a
c
e
e
ca
e
u
ca
s
u
.
Ba i o f Cl ifi ti — M orph o logi l Cl ifi ti — S p fi i l
D epo it — G old Pl er — Ri ver Pla er — I m t i Pl er — B la k
S and B e h e —D eep Le d o f V i t ia — C em ent Pla er — D y
bl owi ng P la r — F orm o f A lluvi al G o ld— A o iate o f A ll vial
Go l d— O rig in o f A ll ial G o ld— S tre m T i — O rigi n o f S tre m T i
— Plati
ia d A m eri a— Iron S and
m P l er — P latin m i R
— G m P l er D iam ond Ru by S app h ire— Ma ive D
Pl
po it — B g Iro —A tion o f De endi g Water —S alt— B orax
— S t t ifi d D epo it — S trike n d D ip o f Bed
G y p m — S l ph
— I l inatio n o f Bed — T h i kne
f B ed — Exam pl e o f B edded
Depo it — C oal— Origi
rr e
d F o rmatio — M od e o f O
A g — In l i ed Po itio n — Fa l ti g — E xt ent o f Fa l t — Intr i e
Dy ke
d th eir Efl t — Irreg laritie — B endi g o f S eam
V rietie o f C o l— R d B anket Ree f — Ma feld Copper S h ale
— S il ver S an d to ne o f U tah — L ead S and tone o f Pr
i Copper
C o gl o merate o f L ke S perior— C oprolite B ed — G y p m Bed
—U
t tifi ed D epo it
Depo it o f V o l ni Origi — S to kwork
D epo it — Conta t d Repl ement D epo it — Fahl b nd — I m
— T r e Fi
—
n
t
i
d
h
S
eg
r
eg
a
te
V
ei
n
G
a
V
ei
Vein
p g
s s
s
a ss
on
ca
s
c
s
ac
ac
ca
a
s
ce
e
ac e l s
s
s
s,
n
u
su
ra
ur
s
e
n
ss
c
n
c
s
e
s
s
a
s
s
s
n
cc u
u
n
u
s
c
ss
o
an
n
a
n
e
s
u
,
sc
r
s
an
u ss
c a
c
s
n
,
c
nc
s
n
u
ac
o
c
a
er
s
ac
ss c
s
u
c or
s
uv
ac
on
ca
cu s r n e
s
s
s
nu
ass
e nc
s
us v
'
s
a
an
s
s
n
n s ra
re
a
s
on s
s
c
s
s
a
an
s
ns
s
s
s
s
an
a
n
s
u
ec s
uss a
u
s
s—
s
ca
s
ac
s
s
Vl l
ns
n
c
s
su
s
c
a
u
s
ss ure
s
s,
P A G
E
C O N T EN T S
CHAP T E R
V E I N S — T H E I R F I LL I N G
ORE
P
F i lli n g
A
,
G E
III
.
U R E WA L L M OV E M E N T S
S T RU CT
S H OO T S ,
A Y
.
,
,
ET C
.
o f C vitie nd Vei — Origin o f Vein C vitie — A g o f Vei
filli g — Wi dth o f L o de — L e gth —S troke — In l i nation — D epth
A rr gem e t o f L ode Matter—Hor e i Vei — O t rop o f Vein
Co ditio o f Metall i Content — Po ition o f Valuable Co te nt
P y S h oot — G o l d Bo na z — Wal l M ov m ents — I fi
of
C
t y — Pro d ti ve Z o e — Verti l D i trib tio
o f Ore
S e o dary E i h m e t o f V ei — I m po e i h m e t o f V ei
i
D epth — I di ator B ed — P rage e i — T em perat re i D eep
M i i g — Re ordi g R ook T em perat re — L i m it f D eep M i ni ng
M t o mati Repl eme t
a
ns
s a
n
n
n
n
-
n
s
an
-
a
a
n
n n
s
e as
c
u
u enc e
s
ns
n
n s s
a
s
n
u
v r s
n
c
n
s
ns
c
s
n
ca
n
nr c
s
e
n s
uc
u c
n
s
n as
ou n i
c n
ns
n
s
s
e
c
s s
c
s
u
n
n
s
s o
s
n
ac
CHAPT ER
T H E D Y NA
MI CS
OF
L
IV
.
on s s
A ND
B
E DS
.
o f Fa lt — Fa lt par llel with B d—D ip F lt — S tep
F lt — T ro gh Fa lt — R le fo In li ed L ode — Z i mm erm n
G raph i M eth o d
D e fi n ition
au
u
s
u
u
s
u
c
s
a
u
s
r
s
n
s
’
a
V
s
.
O S I T S G E N ET I CALL Y
S I D E R ED
CO N
.
g ti eg eg tio C o ite Peri dotite
i ke o
ti e Coppe P ti
et
O e form ed by
pti e A te tio
o t i A tio o A e i g A lkal i e
Water — F ma oli — Cont t M et m orph i D epo it — Regio l
M et m orph i D epo it — M eteori W ter — O rg ni
Cl as s ifi ca tion — M a ma c S r a
n—
hr m
in
— N c l Ir n — N a v
r— la nu m M a l s — r s
Eru
v f r ac n — S l fa ar c — c n f s c nd n
c
n
-
s
u
r
c
c
a
s
ac
s
c
T H E O R I ES
ptive Pro e e —T h eory
tion — S mm y
c ss s
s
u
ar
,
of
OF
VE N
L ateral
S
a
s
a
I
s
c
a
C HAPT ER
Eru
s
,
O R E D EP
e eti
n
c
C HAPT E R
G
au
e
VI
c,
.
FO R M AT I ON
e retio
c
na
s
n—
.
A en io o f S ol
sc
s
n
u
C O N T EN T S
C HAPT ER
O RES
Al
um
A N D
M I N E R A L S C ON
— A l um in i u m — A ntim ony
ix
.
VI I
.
E C ON
S I D ERE D
A r eni
s
O M I CA L L Y
A bes t
PA G
A ph altum
os
s
c
.
s
C opper— Cry ol ite—Diam on d— F irec lay— Fl o rite — G old— G raph ite
— G p sum — Iro n— Lead— Magn e ite— Man gane e
—M l b
M
i
ca
y
y
Petroleum Ph o ph ate R oc k
de a m
O il S h al e
N i kel
Platinum Qui k s ilver S ilver S late S ul ph nr— T alc— T i n
u
s
s
o
s
c
h
c
CHAPT ER
M INE
S
-
AM P L I N G A N D
VI I I
.
O R E -V AL U AT I ON
.
p in g E q ipm ent S am pl i g Interval Rec ord o f S m ple
B reaki g th S m ple — S m p l in g— R ed tio n o f S m p le— A ay o f
P o pec t — S m ple Val e
F t
S am ple — Cal l ating V l
d M i ll Val e — S am p ling D um p
d He p
S am l
n
u
n
s
an
e
a
cu
s
a
uc
a uem
u u re
C HA PT ER
Valuatio n o f
AM I N AT I ON
AN D
s
a
r
s an
u s
T H E E"
a
a
I"
s
s
ss
a
u s
s,
.
VAL U AT I ON
or
MIN
ES
.
M etal M ines — De vel oped M in es a n d G o ing Conc ern s
Class ifica tion o f O re in a M ine — V al ua tio n o f Coa l A reas — Va l ua
I N D E"
E
MI N I N G
G EOL OG Y
C H A P T ER I
.
I N T R O D U CT O R Y
CO N
.
.
ope n d P rp o e o f G eology — G ologi l S tr t r o f
th
Earth— Begi n i g o f Geo l ogi l T i me— T h
A tion o f Wat r i
D e troyi g d Re f mi n h Ea rth C r t m o tly S ed i ment ry
A l teratio n o f S e d i m e tarie — F o il Co nte n t — G eo logi al T i me
Th
marked b y D i ti cti ve L i fe — O rigi o f I g neou R o k — U
fl w Ro k
— D y ke R o k — P l to i B o e — A l t r tio n o f I gneo
R k — M etal
d Mi eral n I gneo
R o k —T h I fl
o f Dy k — Cl ifi ti
o f I gneo R k — I m po rta e o f Petrogr phy
T E N T s z— T
he S c
a
n
s
an
-
n
or
c
n
n c
s i
us
oc
s
us
ss
us
c
s
s
e
s
a
c
s
ue n c e
a
n
c
ver
us
n
e
nc
s
c
e a
ss s
uc u e
s
n
u
s
'
s
n
ca
e
e
n
s
e
ca
e
an
s
n
n
e
u
es
01
o
c
s
as s
s
s
ca
on
.
Th e s t udy of
geology i s unde rta ken by two classes of student Th e r e is the
pa t ient investigator who in th e intere sts of p ure sc ien c e wi t hout
hope of material gain is conten t not only to know t ha t a roc k i s
compos e d of min e ral mat ter but extends h i s researches to th e
investigation of t h e origin compos i tion and structure of th e rock
Then th e re is the ut i l itarian who v i ews a mineral from a com
m e r c ia l sta ndpoint and i s w illing to undergo a spec i al cours e of
tra i n i ng i n orde r to be able to d i stinguish the valuabl e from the
bas e a n d worthl ess
Th e sci e nce may therefore b e divided into Theoretical G eology
which i nves t igate s the or i gin a n d s t ructur e of the rocky crus t of
t h e e art h ; and E conom i c or Mi ning G eo logy which b e ars mor e
direc t ly on m i ning and th e dev e lopment of t h e min e ral i ndus t ry
A knowl e dg e of th e fun dam e ntal pr i nc i pl e s of th e fi rs t is n e cessary
to unde rs tan d t h e s e con d and for th i s reason e v e ry m i ning s tu den t
sho u l d prepare himself for his prof e ssion by going thr ough a
s s t e r a t ic cou rs e i n G e neral G eology
y
n
It i s sa t isfactory to obs e rv e that many of t h e mos t e minen t
mining engine e rs in E urope Am e rica a n d Aus t ralia ar e d i stin
ui s h e d g e ologists
Wha
t
a
n
atomy
is
to
the
modern
surgeon
so
g
i s g e ology to t he mining profession
T he
S cope
a nd
P
u rp o s e
G e o lo g y
of
-
.
.
,
,
,
,
,
,
.
,
,
.
,
,
,
.
,
.
,
,
,
.
.
2
MI N I N G
G e o lo g ic a l S t r u c tu re
of
G EOLO GY
.
E a rth
th e
—
The cr u st of the
earth is th e great r e posi t ory of m i nerals and metals and there
for e a brief consideration of its orig i n and structur e will afford
a bett e r understanding of the ma n ner i n which ore bodies and
mineral deposits occur
B e g in n ing O f G e o l og ic a l T im e G eological ti me date s
back to the fi rs t beg i nning of th e phys i cal co nd i tions w hich now
pr e vail upon the earth To make th i s clear i t will be ne c essary
to trace the evolut i on of the earth to its pres e nt form
Accord i ng to astronomers and physic i sts the earth l i k e many
c e l e st i al bodies at the pr e sent tim e once e xisted as a nebular
mass of glowing in c andescent gases s winging through space B y
the rad i ation of its b e at this globe in t he cours e of countl e ss
ag e s became s u ffi c ie n tly cool for a t hin skin or crust to form on
the ou t er surfac e B y th e cont i nu e d radia t ion of the h e at the
crust became thicker a n d th i ck e r and in a tt e mp t ing to adap t
i tself to the smaller dimensions of the molt e n mass below b e came
crumpled and rucked up into ridges and valleys lik e the sk i n of
a drie d u p appl e
I n the course of time the scarred and gnarled ign e ous crust
b e came cool enough to p e rmit the condensation of the watery
vapours which e nvelop e d th e e arth Th e wat e rs settl e d in t he
hollows and formed the fi rs t seas that ever existed on th e fac e of
th e globe
Th e restl e ss wa t ers of the n e w born s e as at onc e b e gan to wear
away the dry lan d and the streams draining th e valleys t o de e p e n
and w i d e n their channels Th e denu ded material was spr e ad out
in lay e rs a n d b e ds on the rocky fl oo r of the seas t hus marking the
b e ginn i ng of the conditions of sedim e ntat i on that have e xisted
w it hout int e rrup ti on up to the present day Th e se ancient fresh
water sedim e nts wer e the fi rs t r e cords of geological time
.
,
-
-
.
-
.
,
.
.
,
,
,
.
,
,
,
,
.
,
,
,
,
-
.
.
,
.
-
,
.
,
.
T he A
c t io n o f
W a te r in
.
D e s tr o y ing
a nd
R e -fo rm ing
.
F rom t hat date up till n o w water has cont i nued to be t h e most
pow e rful agency i n sculptur i ng and modifying the surface of the
e arth I n wast i ng a n d e roding t h e dry land in transporting th e
e rode d mat e rial i n sorting and spr e ading it ou t the action of
water has b e en unceasing throughout all t i m e
N o portion of t he original igneous crus t or ev e n of th e fi rs t
form e d sed i men t s has ever b ee n found 5 but shr e ds and patches
may still ex i st buri e d beneath t he deposits of lat e r t i m e s
Th e amount of matter forming th e e ar t h is prac ti cally a fixe d
quanti ty ; h e nc e it is e vid e n t that all the d e pos i ts and b e ds now
forming t he surfa c e of the e arth must hav e been derived from t h e
d e s t ruc ti on of the fi r s t igneous cr u s t or of sedime n tary rocks of
,
.
,
,
,
.
,
,
,
.
,
later date
.
INT R OD U CT O R Y
3
.
E v e r sinc e t he b e gi n ning of g e ological time the dry land h as
be e n d e nud e d by wa te r yieldi ng the ma t erial to form ne w depos its
in seas and lak e s Through the contin u al crumpling of th e cr ust
of th e e a rth th e se d e posi t s in course of t ime beca m e dry land
and in t he i r turn were subj ected to the ag e nts of erosion aga i n
yi e ld in g ma te rial to form s t i ll n e wer de pos i t s or s tra ta This
t h e older formations pro viding th e material
a c t ion i s still going oh
for th e youn g e r
Th e sa m e mat e rial has app eare d r e sorted in di fferen t fo rms i n
diff erent geolog i cal ag e s It is now ea sy to und e rsta nd how some
of th e older forma t ions have been entirely remove d by t his ever
last i ng denudation or are represented only by isolated remnants
,
.
,
,
,
,
,
.
,
.
-
,
.
,
of small extent
.
C ru s t m o s t ly S e dim e n ta ry — A
exa m ina
t ion of the crust of t h e ea rt h shows that it is c omposed p rincipally
—
of s tra tifi e d rocks t hat is rocks occurring in parall e l bed s or
layers A stu dy of the materials forming th e s e roc ks and of the i r
fossil cont e n t s shows u s t hat t h e y hav e be e n formed by t h e
gradual depos it of s e dimen ts on the fl oo r of some sea or lake in
some cases by precipitation f rom solutions or by the growth and
a ccumulat i on of animal or v e ge table organi sms
Th e physical s t ruc t ure of sedimentary or clas t ic rocks— as t h e y
are some ti m e s called — i s depend e nt on three main fac tors nam e ly
the textur e of th e mater i al the charac t er of th e cemen t ing
medium and the amount of i ndura t ion alte ration or m e ta
morph i sm to wh i ch th e mat e rial h as b e e n subj e cted
Wa t er has possess e d through all t im e t h e sam e eroding trans
por ti ng and so rting power and what w e now s e e go i ng on in our
vall e ys a n d on our shores i s a fair exampl e of what took pl ac e in
earliest g e olog i cal ti m e
Th e grav e ls on the shores formed conglom e rates t he water
born e sands formed sandston e s t h e mor e d i stan t muds beca me
shales wh i le the l itt oral shell beds and coral reefs b e ca me lime
ston e s
—
T h e A l t e ra t io n O f S e dim e n ta rie s
The ol der sedimen ta ries
hav e be e n subj e ct to all th e la t er mov e ments wh i ch have affe cted
t he crus t of t he ear th Th e y hav e b ee n indurat e d by t he gr e at
we i gh t of sup e rincumben t s t ra ta plica ted a n d con to rt e d by
e n tangl e m e n t i n grea t ear th folds and alt e red by the s i multa neous
act i on of pr e ssur e h e a t and c i rculating th e rmal wa t ers Thus
l i mes ton e s hav e b ee n changed to marbl e s sandstones to quar t zi te
muds tones and shales to slat e s or schis t
F o s s il C o nte n ts — E xamina ti on h a s shown that th e earl ie r
e xis ti ng stra ta con ta in a f e w ind i stinct and badly p res e rved
rema i ns of plants and an i mals of a very primi t ive and lowly type
T h e E a rt h
’
s
.
n
,
,
.
,
,
,
.
,
,
,
,
,
,
.
,
,
,
.
-
.
.
.
,
-
,
,
,
.
,
,
.
.
.
MININ G G EOLOGY
4
.
Beds highe r in the su c cession are found to contain a large and
varied assemblage of plant and animal remains many of a highly
compl e x stru c tur e such as molluscs fi sh e s huge bird like lizards
saurians palms and tree ferns Th e higher or younger depos i ts
contai n besides molluscs and fi s h e s the remains of many
mammals wh i ch have r e presentatives living at the present tim e
I n other words th e re has been a gradual succ e ssion of life in t i m e
from the lowly to the more highly organised forms
—
G e o lo g ic a l T im e m a rk e d b y D is tin c tiv e L ife
Ex
h a u s tiv e i nvestigation has shown tha t c ertain o r ganic forms occur
only in certain beds S uch fossils are termed characterist i c or
d i stin c tiv e fo rms G eologists have taken advan t age of these to
divide g e ological time into periods j ust as histori c t ime is divided
into periods by succeed i ng dynasties or empires These periods
are pur e ly e m pirical and are used for c onvenie n c e of des c ription
and study
G eological time embraces three great periods which are further
subdivided as shown below
Recent
,
-
,
,
,
,
-
.
,
,
,
,
.
,
.
.
.
.
,
.
,
.
,
.
T E RT I AR Y or Cainozoic
Pliocene
M iocene
E ocene
,
.
.
.
SE C O N D A R Y,
Cr e taceous
or M esozoic
J u ra ss ic
Triassic
.
.
.
Permian /
Carboniferous
.
P R I M A RY ,
D e v om a n
or Pal aeozoic
.
.
Silurian
Cambrian
“
L aurentian
.
.
.
Su c h terms as Permian D evonian etc ar e time names
cover vast eeon s When a ro c k is said to be of Mi ocene age a
reference to the table will sho w that it is comparatively young
whereas a rock of S i lurian age is one of extreme antiquity F or
purposes of clos e inv e stigation these time periods ar e sometimes
st i ll further subdiv i ded by geologists
—
r
i
i
n
O g
Throughout all time the outer
of I g ne o u s R o c ks
shell or crust of the earth has been subj ect to the in t ru s ion a n d
o v e r fl o w of molten magmas from below ; and there is abundant
evid e nce tha t these igneous intrusions or outbursts were more
frequent more v i olent and more widespread in earlier than in
,
,
.
,
,
.
,
.
,
.
.
'
,
,
MININ G G EOLOGY
6
.
of s u perheat e d steam has often caus e d a rearrang e ment of th e
cons t ituents 5 while th e circula t ion of th e rmal waters has led to th e
elimination of some and the substitution of other constituents
of secondary origin
M oreov e r it is found that intense meta
morphism may cause alter e d lavas and tu ffs to assume a sch i stos e
structure not unlike that induced in altered sedimentaries
—
M e ta l s a n d M in e ra l s in I g n e o u s R o c k s
N o volcanic
ro c k of recent date is known to contain m etall i f e rous deposits of
commercial valu e Traces of gol d silver and most of the base
me tals have been found in modern lavas ; but the only minerals
of economic importance associated with these rocks ar e sulphur
and gypsum both of se c ondary origin
The M iocene andesitic lavas and tu fl s of the Sie r ra N evada and
Cripple Creek districts in America 5 Transylvania and Banat in
Hungary 5 of Borneo and Sumatra in M alaysia 5 and of Hauraki
Peninsula in N ew Zealand contain gold and silver bearing veins
of great value in which ores of c opper lead and zinc a r e some
times pr e sent
A fl ow of andesite near the M anukau Heads in N e w Zealand
contains large grains of native copper an o c currence which is
rare and ther e fo re of great s c ie n tifi c inter e st
V olcani c tu fi s and lavas are also the m atrix of diamonds opals
and other precious stones
T h e I n fl u e n c e o f D y ke S — D yke rocks are not often them
selves metalliferous 5 but they have exerc is e d a potent in fl u e n c e
on the distribution of metallif e rous deposi t s M any valuabl e
v eins of gold and copper occur in t h e vicinity of dyk e s 5 and
although t h e re is little de fin ite knowl e dge concerning the origin
of v e in matter it s e ems fair to assume tha t the intrusion of the
dyke material originated fractures and fi s su r e s in the adj acent
c ountry which then became channels or tracks for the c irculation
of mineral —laden wate rs
I ntrusive bosses suc h as those of granite are oft e n impregnated
with tin ston e near the contact wi t h sedim e n t ary s t rata ; and in
other cases the sedimentary rocks in the n e ighbourhood of th e
granite are traversed by valuable veins of tin and copper
The association of tin veins and granite bosses is too frequent
to be a mere coinciden c e 5 and we ar e comp e lled t o conclud e that
in some way which is not very clear to u s t he vein and its
contents are connected with th e presence of th e boss
Th e int rusion of the boss may possibly have til t e d and fractured
the surrounding rocks 5 or th e boss may hav e been the anvil
against which the softer and more yielding sedimentaries were
crushed and fractured by the lateral stresses initiated by the
se c ular folding of the c rust of the earth I gneous magmas are
,
,
.
,
.
.
.
,
,
,
.
'
-
,
,
,
,
.
,
.
’
,
,
.
.
.
-
,
-
,
.
,
,
-
,
,
.
,
,
.
.
IN T R OD U CT O RY
7
.
cha rged wi t h water and gas e s D ur ing the process of cooling
mos t of t he wate r and gas e s ar e e xpe ll e d as highly hea t ed s te am
and
as will b e shown la te r on t h e r e i s much e vi de nc e to
s uppo r t t h e b e l ie f tha t t h e
s t eam a nd gas e s w e r e laden w it h
d issolv e d me tals which wer e af te rwa rds d e posi t ed in t h e zon e of
.
,
,
,
,
F or ou r pre s e n t pu rpos e s
i n three principal and e as i ly dis
C las s ifi c a t io n o f I g n e o u s R o c k s
igneous rocks may b e c lass ifie d
tin g u is h a b le gr ou ps as foll ows :
C la
.
c
.
Basic
I nte rmedia t e
.
.
Ba sa lt
Andes ite
Tra
m
(
m
b
Rhyoli
t
e
( )
,
Ac i dic
,
Vo lca ni c T y pe
ss .
A
B
—
.
.
”
,
,
.
.
The types wh i ch have proved
diori te and e si t e and granite
,
mos t productive ar e diabase
th e
,
.
,
P et rography was form e rly a
narrow branch of gen e ral geology Oi late years i t has de
w
v e l o ed into a d istinct sci e nc e wh i ch conc e rn s it s e lf c h ie fl
i
t
h
y
p
t h e minu te structur e compos it ion a n d nom e ncla t ure of i gn e ous
and crys ta llin e rocks a n d al t hough th e general i sa t ions of p et ro
graphy hav e l ittle bear i ng upo n t he ph e nomena of s t ruc t ural
g e ology i t is ne e dful t ha t e v e ry geolog i s t should have an
i ntima te knowl e dge of its l e ading f e a t ur e s
Val u able m i nerals a r e so frequ e n tly ass ociated wi t h i gn eous
rocks that it seems imposs i ble to avoi d the c onclusion t ha t a clos e
g e n et ic r e la t ionship exists b e tw e e n t h e m What th i s r e la t ion s h i p
r e ally is has y e t to be de t e rmin e d in th e maj or ity of or e
deposits
Ro ck forming constituen ts are now known to s e pa rate in t h e
coolin g magm a i n a de fin ite order and t h e inv e s ti ga t ion of t h e
laws gov e rn i ng magmat i c d i ff er e n t ia t ion prom i ses t o throw much
—
l i ght on the gen e s i s of ore d e pos i ts
I m p o rt an c e
Of
e t ro g ra p h y
P
—
.
.
,
,
,
,
,
.
.
.
-
,
.
C H A P T ER I I
D E P OSI T S
MI NE RA L
C LA S S I F I C A T I O N O F
C ON T E N
.
.
B i o f Cl sific ti
M ph l g i l C l ifi ti
S
—
—
—
G
l
R
l
D
epo
it
o
P
e
r
i
v
e
r
P
e
r
L
tri e Pl r
l
d
i
l
s
fi
S p
— B l k S nd Bea h e — D eep L e d o f Vi t n — Ce me t P l er — D y
b l o wi g P l er — F orm o f All vial G old— A o i te o f A ll vi l G o l d
O igi o f A ll vi l G o ld— S t e m T i O rigi n o f S tr am T m — P l ti
P l er — Pl ti m i R ia d A meri — Iro S nd P l er — G m
Pl er D i m o d R by S pph ire— Ma i ve D epo it — Bog Iro
A tio f De e ding Water — S l t — Bor x — G y p um — S lph r
—
D
epo
it
i
d
S trike
n d D ip
f B e d — I c l i ti n o f B ds ?
St t fi
o f B ed — Ex m ple f B edded D epo it — Coal — Origi n d
T hi k e
F or matio — M o de o f O
r ence— A g — In l i ed Po itio — F lti g
Exte t f F l t — Intr i e D y ke
d th ei r E fl t — Irreg l riti
feld
B e din g o f S e m — Varietie o f Co l— R d B k t R ee f — M
Coppe S h le — S i lver S nd to e o f U t h — L d S d tone o f Pr i
— C opper Co gl o m r te o f L ke S perior— Copro l ite B d — G p m
f V o l n i O rigi — S to w o rk
t t ifi d D epo it — D epo it
B ed — U
D epo it — Co t t d Rep la m t D epo it — F h l b n d — I m preg n
tio — S egreg ted Vein — G a h V i — T r e F i re Vei
—
T he
T
on
a
ac
s
c a
er
u
as
as s
o o
or
w
n
ac u s
s
ac
s
on
ca
a ss
ca
ac e s
’
s
ac
s,
n
a
n
c
s
n ss
c
u
,
s
s
a
s
n
n
s
n
a
r
n s ra
s
a
e
ns
a
s
a
n
s
an
ca
s
e ns
s
s
s
u ss a
ss u
u
sn
s
n
c
a
es
ans
s
e
o
a
ns
a
n
au
u a
e
ea
en
ce
s
s
e
n
u
s
an
o
s
an
a
a
‘
ec s
an
u
u
na
n
an
n s
s
s
c
a
s
e
n ac
s
s
s
s
n
s
us v
s
a
n
s
e
n
s
s
e
s
s
s
o
s
cc u r
au
o
o
a
ac
a
a
a
n u in
a
ss
a
,
n
ca
r
a
u
e
an
uss
sc n
o
e
ra
n
s
ac
s
c a
n-
r a
nu
a
ac
n
a
ss
u
a
u
n
r
c o
s
a
s
s
ac
n
s
c
a
ac
c
s
a
.
—
f
M inera l
o
C las s ifi ca tio n
d e posits are found
in so many di ffe rent forms and und e r so many varying con ditions
that t he attempts of different writers to formulate a c la s s ific a tion
found e d upon a natural basis have not b e en attended with much
success I n any case it must be r e memb e red that a c la s s ifi c a tion
i s only an e mpiri c al arrangement intended to facil i tate the study
and investigation of min e ral d e posits
The maj ority of the c lass ifica tion s hitherto proposed are based
upon either (a ) morp h ologica l or ( b) g en etic consi de rations or ( c)
a comb i nation of the two
The fi rs t principles of ore d e positio n are st i ll imperf e ctly
understoo d The most diverse th e ori e s ar e still advanced by
em i n e nt authori t ies ; and it is doubtful if a theory has y e t been
for rn u la t e d that will sat i sfy all the cond i tions and explain all the
iacts
The basis for a natural c la ss ific a tion has still to b e discovered
U n ti l then outward form and mod e of o c currence seem t o
B as is
T he
.
.
,
,
,
,
.
,
.
,
,
.
-
.
r
.
.
,
8
C LA S S IFI C A T I O N
OF M I
NE R A L D EP O S I T S
9
.
o ff e r the mos t conveni e nt sta rting poin t for th e el e mentary
-
Th e more advan c e d s t udy that is the philosophical inquiry as
to t he origin p e rs i stenc e a n d probabl e valu e of or e d e pos its can
only be pursued wh e n some knowledge h as b e en acquir e d of th e
fun damen tal laws of or e forma t ion I n t h i s case t he inv e s ti ga t ion
mus t b e pu rsued from the g e n et ic standpo i n t
I Ve w i ll firs t deal with mineral d e pos i ts from t h e mo rphological
and aft e rwa rds from the genetic standpoint
,
,
,
-
,
,
-
.
.
.
M O RPH O L O G I CA L C L AS S IFI CAT I O N
.
simpl e c las s ific a tion of v e ins and mineral de posits bas e d
upon out wa rd form and mod e of oc curr e nce but e ntir e ly in de p e n
dent of ag e or mineral charac t er is as follows
A
,
,
,
Cl a ss l — S u pe rfi c ia l
—
Class II S tra tifi ed
Class III — U n s t ra tifi e d
.
.
.
.
.
.
F or descriptive purposes thes e clas ses may be subdivided into
,
groups or sub cl a sses
-
,
as
—
I
.
( )
b
( )
a
u
nder
D EP O S IT S
S U P ER F I C I AL
F r a g me n ta ry— F orming all uvial drif ts
M a ssi ve— F orming laye rs and sheets
.
.
I I S — S T RA T I F I ED D E P O S I T S
( )
formation
b
D
i
s
e
m
i
s
n a ted
( )
a
.
—
bed s
Con stitu ting
.
F o rming m e mbe rs of a
.
th ro u g h a bed
I II
—
.
.
U N S T R AT I F I ED
D EP O S I T S
.
D
e
o
s
i
t
s of v ol c a n ic or ig in
p
( )
b
t
k
o
S
c
w
o
k
d
r
ep os its
( )
( 0 ) Con ta c t a n d r ep la ce ment dep os its
d
F
l
a
h
b
n
a
d
s
)
(
a
.
.
.
( )
(f
(g )
h
( )
8
G
T
as h v ein s
r ue
.
fi ss ure
v e ins
.
.
s t ra t ifi e d
MINI N G G EOLOG Y
10
CL ASS
.
I
SU P E R FI C I A L D E P OSI T S
( )
a
F rag me n ta r y
.
.
These embrace alluvial deposi t s
f
of all kinds whether beach sands river gravels lake deposi ts or
glaci e r drifts containing loose particles of gold tin ore pla t inum
iron ores or precious stones They also includ e the alluvial deep
leads or deep placers of California V ictoria and N ew S outh
Wales which are often cov e r e d with a sheet or sheets of basalt
D efinitio n
P la ce r D ep os ita —
o
,
,
,
,
-
,
,
,
,
.
,
,
,
,
,
.
,
G o ld P la c e rs
.
That po r tion of the drift in whi c h the gold is c o n centrated is
termed p a y wa sh p a y dzr t or p a y s trea k When the pay wash is
covered by a considerable d e pth of gravel —drift or other cover it is
termed a deep lead
M e th ods of working P la cera — Alluvial drifts a cc o rding to thei r
situation are worked as follows
1
B
ground
or
gravitation
sluicing
with
water
not
under
)
(
y
pressure
— tha t is ground sluicing with water under
2
B
hydraulicking
( ) y
pressur e
3
B
hydraulicking
and
elevating
wi
t
h
water
under
pressur
e
y
( )
This method is only resor te d to wh e n the con fig u ra tion of the
ground renders it impossibl e or too costly to construct a tail race
for gravitation sluicing I t is worked wit h much success at the
Blue Spur and o t her claims in Ne w Zealand
4
B
( ) y bucket and suction d redges when the mate rial is mainly
or partly b e lo w wat e r level as for example on sea beaches mari
time lagoons lakes rive r beds and river fl a ts
E xa mp les of G old P la ce rs — F amilia r examples of gold bearing
gravels are the alluvial drifts of V ictoria W e st Aus t ralia Klon
dyke California Ne w Zealand and Altai M ountains in C e ntral
Sib e r i a
—
G old b earing beach sands containing iron sa n d mostly magnetite
occur along th e shor e s of Westlan d and Southland in N ew Z e aland
and the G old Coast of West Afr i ca
Among later alluvial gold discoveries that at Cape N ome in
Alaska is th e mos t important A sloping plane or tundra extend s
from the s e a back to th e foot of t he mountains I t cons i sts of
a succession of b e ds of sand gravel and clay res t ing on the
upturned edges of the Pal aeozoic basem e nt roc k The su rfa c e is
’
-
-
-
-
,
,
.
,
-
.
,
,
.
,
.
.
-
,
,
.
.
,
-
-
,
-
,
,
,
,
-
,
,
.
-
.
,
,
,
,
,
,
.
-
,
,
,
,
.
,
,
,
.
.
,
,
.
C LA S S IFI C AT I O N
MIN
or
ER
AL D EP O S I T S
11
.
covered with a layer of tundra moss and decaying vege ta ble peaty
matter to a depth of 18 inches or 2 4 inches Th e gold b e a ring
matter is foun d along the beach being appar en tly a rewash or
oncentra
t
e
of
the
tundra
gravels
and
sand
c
T h e tundra gr avels bear no e vid e nc e of glacier o r igin bu t
appear from th e ir bedd e d and wate r—worn ch ara cter to have b ee n
de posited in a lake—b a sin or in a shallow sea n e ar th e estuary of a
large r iver
G lacier D r ifte — Count ry that was once overrun by glacie rs is
to contain two classes of tra n spo r ted matter — on e trans
-
.
,
.
,
'
.
FI
G
l
.
.
— S ectio n o f G lac ier abo ve
( a ) M orai nes
( b)
B ement ro k
c
as
(c)
.
(d )
.
ermi al F e
G lacier tu n l
Gl i r i
T
n
ac
n
ac e
ce
e
.
.
.
porte d by ice the other by water The fi rs t forms tumbled
morainic m a sses the latter water worn gravels and sands deposited
.
,
-
,
FIG
.
2
.
— S ectio n o f G lac ier Valley
( at ) G lac ier m o rai nes
( b) G lac ier grave ls
.
(c ) B as e ment roc k
( d ) G lac ier ri ver
.
.
.
.
by the river which dra ined the botto m of the gla c ier Both
class e s are o ften mixed a t c e rta i n points When th e co un try i s
gold bearing the glacier gravels and morainic matt e r conta i n gold
The mo ra i nes are formed by ic e which cannot s e para te th e gol d
from the rock debris ; hen c e the gold is scatt ered thr ough i t j us t
as the glacier happ e ned to drop it The gl a cier gravels on t he
.
.
-
.
,
.
,
12
M I NIN G G EOLO GY
.
other hand being larg e ly a rewash of the moraines c ontain the
gold in a more conc e ntra t ed form
M any of the gold bearing t erraces in N ew Zealand a nd in the
h i gh e r valleys of the Rocky M ountains bear e vi dence of glacier
r i ver orig i n while som e are compos e d of a rewash of glacier
grav e ls and morainic matter
P os ition of P a y Wa sh
E xperien c e has shown that alluvial gold
i s deposit e d along the inner side of the curves in the course of the
river Any stratum of good grav e l in the opposite bank was
e vidently laid down at so m e pr e vious time under similar conditions
The accompanying diagram (fig 3) shows the distribution of th e
pay wash Th e gold is coars e st at the h e ad of the bar gradually
b e coming fi n e r and s c arcer and spreading ou t below until th e
dirt is too poor to pay 8 0 long as the river r e tains its course
,
,
.
-
,
.
-
-
.
.
.
,
.
-
.
,
,
,
.
FIG
.
3 —
.
,
P lan o f R i er cour
v
se , s h o wm g
-
po ition o f gravel
s
s
.
th e pay streak will continue to form as the bar is ext e nded
y e ar to year
Th e average uniform size of the gravel seems to show that th e
gold i s only deposit e d where the current has a cer tain medium
velo c ity A t the points wher e th e bends in th e river ar e mad e
more permanent by rocky banks th e pay gravel is generally deep e r
and of greater ext e nt than elsewh e re
The richest gold does not collect in the de e p pot holes in th e
river as might naturally be expected but on t h e bars or rocky
l e dg e s below The reason for t his may be that pot holes g e ner
ally occur in narrow rock bound parts where the v e locity a nd
scour of the water are t oo great to p e rmit the p e rmanent
lodgment of the gold particles
P os ition of G old in D r if te — I n alluvial deposits the gold is
foun d in a layer of pay wash resting either on t h e s la te or s ch ist
I n r iver and creek workings th e
bottom or on a fa lse bottom
-
.
.
-
,
.
-
,
,
-
.
-
,
.
-
-
,
.
,
14
G EOLOGY
MI N l N G
.
been tilted almost on edge thereby greatly in c reas i ng the diffic u l
ties of work i ng th e pay wash with success
B l a c k S a n d B e a c h e s — The washing of b e a c h sa nds is a
for m of alluvial m i n i ng pu rsued on the sea b e aches of Westland
and Sou thland in Ne w Z e aland The black sa nd is princ i pally mag
n e tit e d e rived from the disint e gration of the neighbouring rocks
The gold occurs in excessively fi n e particles and is found con
the
c e n tr a t e d wi t h the black sand in layers along the sea beach
laving act i on of the r e tr e ating waves removing the lighter par
t ic l e s of quartz sand
D e e p -L e a ds o f Vic t o ria — The buried placers of this sta te
are of great ext e nt and value They may be ta ken as typi cal of
a c lass of d e posi t also found in California They consist of gold
,
-
.
.
-
.
.
,
,
.
.
.
.
FIG
.
6
h o wi ng L acu strine G old bearing Wash ( A fter Park )
( a ) Rece n t g ravel s
( d ) Carbo n aceou s san ds
( e ) G o ld b eari n g wa s h
( b) Gray q u rtz s a n ds
( c) Ferrugi n o us qu artz sa n ds
( f ) S ti ff c lay
( g ) S ch i s t
.
— S e ctio n
s
-
.
.
.
.
-
a
.
.
.
.
.
bearing gravels c overed by a single fl o w of basalt or by a succession
of thin flows separat e d by b e ds of gravel
The gold bearing pay wash lies on the fl oor of an c ient river valleys
i nto which the lava streams poured from crater vents and fiss u re s
situat e d in the higher lands T h e ancient valleys when c ompara
t iv e ly narrow were g e nerally fi ll e d w i th the ign e ous magma to
such a d e pth as to cause the dive rsion of the str e ams in t o n e w
channels I n some cas e s the area was invad ed by fl oods of
lava which ov e rfl owe d the d i str i ct for hundreds of squar e miles
a n d bu i lt up great basaltic plateaux on the sites of the river
valleys and watercourses
Wh e r e t h e r i ver valley down which the lava pou red was wide
the magma g e n e rally spread itself over t h e gravels in a thi n
stream Th i s caused only a temporary or partial dive rsion of the
river in s u ffi c ie n t i t would seem to compel the river to fin d a new
outlet in another river system
,
.
-
-
-
-
.
.
.
-
,
.
,
,
,
-
.
.
C LA S S IFI C A T I ON
MINER AL D EP O S I T S
or
15
.
Where a success ion of g ravel beds and basalt fl ow s occurs
may b e inferred t hat t he t hin fl o ws only t empora rily div e rted
w h i ch ma intained i ts o riginal wat e rshed un ti l the
ion of material had re a ch ed such a h e ight as to com
,
CA M P
s rn c r
(
F I G 7 —C ro ss
.
un
e tion o f B
derly i n g b
lt
-s
c
a sa
a
HI L L
J DI A R D
'
rat G oldfie ld s h o wi ng deep le
( A fter R B rou g h S my th )
lla
.
-
,
.
.
chok e u p the old valley wher e by the wate rs were enabl e d
to command a n e w ou t let t hrough some low saddl e or pass i nto a
neighbouri ng wat e rs hed
S i nce th e em i ssion of the ba sa l t s the coun t ry has b e en di ssec t e d
l
e
t
e
l
p
y
,
.
WIN
a n'
FI
G
.
u
m »
S rk t
‘
FL A 1
t r
e tio o f Deep le d B ll rat G ldfi l d h o wi g
e io n o f
lav fl w
d ri er g ravel
( A fter R B ro g h S m y th )
8 —S
.
fl u ll c n u n
?"
n
c
a
o
s an
-
v
a
-
a
aa
s
e
o
.
.
,
s
n
u
s u cc
ss
.
by streams a n d sc u lptur e d into the e xist i ng ri dges plate aux and
valleys I t is no t ic eable t ha t t h e new r i v e r cours e s are s e ldom
coinc i d e nt w i th th e old wh i ch s ti ll l i e bur i ed und e r their load of
gravel and basalt exc e p t at th e po i n t s wher e t he i r cours e has been
c rossed by th e ne wer t ransve rse streams
,
-
.
,
.
,
MININ G G EOLOGY
16
.
This process of denudation h a s in some c ases removed th e
barriers which bounded the ancient riv e r valley Thus the fl oor
—
fi
a
t
of the old valley with its cap of hard basalt now forms
topped
ridges wh i le the hills wh i ch formed the barriers have b een worn
down into valleys and water c ourses
-
.
,
,
,
.
b
a
FIG
.
ection o f M o nt Gree o k h wi g protective effe t
o f ba lt p ( A fter R Bro gh S my th )
l
s
d
l
W
d
a
i
r
t
W
a
i
r
t
e
r
i
g
b
a
a
t
h
h
d
)
( )
y
e
E xi ti g w t r o
(d ) Ex i ti g waterco r e
S
9
-
.
ca
sa
(
a
n
u
s
-
s
n
c
.
,
s
u
.
.
s
c
.
a e c
u rs
c s
n
o
n
s
.
n
un
-
u s
.
.
The pay wash in the deep—leads of V i c toria generally lies at th e
base of t h e buried gravels resting in a rocky gutter or channel c u t
i n the bas e ment rock
-
.
FIG
.
10 — S
.
e tion o f Deep Le d i D y le ford D i tri t h o wing po itio n
o f gold beari g w h ( A fter R B S my th )
-
c
a
n
-
n
as
a
s
s
.
.
.
c
,
s
s
.
The d ee p leads accord i ng to the contour of the ground are
worke d by shafts or from adit levels
—
m
C e e nt P la c e rS
G old bear i ng grav e ls have sometimes
become consol i dated into hard cements or even conglomerates
by th e cementing a c t i on of iron peroxide carbona t e of l i m e or
s l i ca deposited from waters whi c h at one t i me circulated through
t em
Ce m ented placers are found in all g e ological formations from
the S i lurian up to the pres e nt day The most important a r e of
recen t a n d young e r T e rt iary age
T h e quartz grits and conglom e rates which form t h e coal
measures of the M ioc e ne brown coals of N ew Zeala n d are gol d
bearing throughout O tago Westland and Ne lson ; but only in a
f e w places ar e t h e y rich enough to be wo rked for thei r gold con te n ts
-
,
,
-
,
.
-
.
,
,
,
i
,
.
“
.
.
,
,
.
C LA S S IFI C AT I O N
MIN
OF
ER
AL D E POS IT S
17
.
Th e i mpo rtance of t h e se old pl a ce rs lies ma i n ly in the c i rc ums tanc e
tha t many of the richest pl ace rs of a rec e n t or Pleistoc en e da t e
deriv e d their gold from them by a proc ess of na t ur al c oncentrat i on
C e m e nted gold bearing gravels mostly s u p e rfi c ia l are comm on
e nough in all alluvial fi e lds and many notabl e examples ar e found
in Californ i a and Central Sibe ria more es pecially in old river
chann e ls
G old b e ari ng cements of a unique kind oc cur a t K i ntor e
Kanowna Kalgoo rli e a n d e lsewhere i n We s tern Aus t ral i a Th e y
d i ffer fr om th e fl u v ia tile wa te r worn gr avels wh i ch form th e
l
c e ments in N ew Zea land and Californ i a Ac c o rding to R ic ka rd
th ey consis t variously of in te rmingled clays sands gr i t s kaolin
"
.
-
,
,
,
,
.
-
,
.
,
,
-
,
.
,
P
H}
c
.
.
n
.
c
n
a
ar
-
.
n
,
s
s a
a an
e
,
a
.
,
n
s
.
.
n
.
ss
c
a
1
2
3
4
,
e tion a ro S late Ri ver Co ili g wood N w Z e l d h o wi g
go ld be ri g ement belo w e m o f c oa l ( A fter P rk
Quartzites
go ld be ring ceme t
B ro w c o l ly i g
G o ld be i ng egregated q rtz vei th e so rce o f gold in cement
11 — S
.
,
,
Qua i tzite s
on
-
a
ua
s
n
-
n,
.
s
u
.
.
broken rock iron s tone and qua rtz in most cases r esting in
2
shallow depre ssions
Th e ir o ri gin i s due to pe c uliar geologi cal and c l i matic conditions
Th e surfac e h as been expos e d to
T h e cl ima te is s e mi trop i cal
sub a e rial in fl u e n c e s sinc e probably th e e arly pa rt of t he S e condary
e
rio
and
i
s
des
t
itute
of
running
s
t
r
e
ams
The
ma
te
r
i
als
d
a
r
e
p
t he prod ucts of long cont i nued a t mospheric d isintegration a n d
erosion ; They wer e transpo rt ed to th ei r present plac e s by the
a ct i on of wind rain and fl ood waters
I n no case has th e ma te r i al
or con ta i ned gold travell e d far from the parent sourc e The
w ork i ng of the c e men t s a t Kalgoorli e l e d to th e dis c overy of t he
more valuable lode formations
-
,
,
.
.
-
.
,
,
,
.
-
-
,
,
.
,
,
.
,
,
-
.
1
T
A
R
i k rd
A
“
T he
ll u v
A m I n st M i n E ng , v ol xx v iii
2
B 1a tc h ford, B u ll etm N 0
T
er h , 1 8 99
.
.
.
P t
.
c
a
.
.
.
,
.
.
ial D epo it o f We ter A tr l ia
s
s
s
.
.
3,
G
eol .
S u r vey
f
o
n
us
a
Wester n
A
,
T r a ms
u s tr a l za
.
.
MININ G G E OLOGY
18
.
—
l
o
A s a r esult of the long continued
D ry b w ing P la c e rs
sub aerial disint e gration the surface of the fl a t country around
Kalgoorlie has b e com e covere d by a d e posit of red sandy loam
ben e a t h wh i ch there is oft e n blu e clay This material which occurs
most fr e quently at the h e ad of shallow gulli e s i s mix e d wi t h
frag m ents of iron ston e and a l i t tl e quartz d e rived from the gol d
bearing lodes l n th e vicinity
The gold i n th i s loos e sur face material 18 obtained in the absenc e
of water by th e method peculiar t o Australia known as d r y
blowm g wh i ch consists of screen i ng shaking and dry blowing
( Plate L )
—
F o rm s o f A l lu v ia l G o l d
E xcepting the large r nugg e ts
which have been found of all shap e s and sizes up to thousands
of ounc e s t h e coarse gold g e n e rally assumes a bean—shaped
form
The fi n e r gold occurs as small heavy shots but more often as
thin fl ake s ranging from the smallest particl e which almost fl oa ts
in wa t er to pieces l i ke bran
I n riv e r claims where the gold has been deriv e d from the denu
dation of gold bearing lodes fragments of quartz with a dhering
pi e ces of th e precious metal are often met with
—
The constant asso c iate of
A s s o c ia te s O f A l l u v ia l G ol d
alluvial gold i n all countri e s is magnetit e sand the agenci e s whi c h
led to th e c on c e nti a tion of the gold having also collect e d th e mor e
abundant magn e tite I t is found t hat whatever h e avy or e s or
m i nerals ar e associated w i th the gold 1n the original country rock
are also found wi t h it in the r e sul t ing alluvial drift s
I n Collingwood in Ne w Zealand considerable quantiti e s of
na ti ve lead i n the form of round sho t have b ee n found for many
years in the slui c e boxes with the gol d
I n places it i s so
abundant as to choke up the rippl e s Samples collected by th e
author and submitt e d to ch e mical e xaminat i on disclose d the fac t
that t h e l e ad is almost chem i c ally pure and somet i m e s e ncloses a
skeleton of gold
I n Takaka near Collingwood the alluv i al gold besides magn etite
is as sociated with gray Coloured grains of osm i um ir i dium a n d
platinum ; in O repuk i with one ounce of platinum for e very
hundred ounces of gold 5 on the West Coast and in the fi or ds wi t h
garn e ts locally known as rubi e s 5 and in Central O tago with large
mass e s of sch e el i te and m agnetit e
Throughout Austral i a the alluvial gold is oft en associated
with gem sands containing t opaz zircon spinel rubies and
garnets
O rig in o f A ll u v ia l G o ld
Alluvia1 gold originat e d from th e
we a thering and denudation of country containing gold bearing veins
-
-
.
-
,
,
,
.
,
-
.
,
,
,
.
-
,
,
,
,
.
‘
,
.
,
,
.
,
,
,
,
.
,
‘
-
,
.
.
,
.
-
.
,
,
,
,
,
.
.
,
,
,
.
,
,
,
,
-
,
,
,
,
.
,
,
,
.
-
.
-
,
20
MININ G G EO LO GY
M
S T RE A T I N
O rig in
S tre a m T in
Of
.
.
—S t ream tin or i g i nated
from the
surface disin t egration and denudation of tin bearing lod es or of
granitic mass e s containing tin impregnations
T h e T in P l a cer s of M a la y s ia —The tin fi e lds of M alaysia are
—
of great extent and value the tin beari n g belt extending south
w ard from Burmah and S i am through t he M alay P e n i nsula to
t he outlying islands of Banca and Billiton o ff th e sout h e ast coast
of Sumatra
The tin bearing gravels are deposit e d on the fl o or of th e valleys
which in t ersect th i s rich zone of metall i ferous country
The geolo g ical f e atures throughout are almost the same The
basement rock is granite which i s variously overlain by gneiss
1
schis t sla ty shales sandstone and limeston e
Tin stone has been
found in situ in veins traversing both the granite and slates and
disseminated as impregnations in the granite near the contact
2
with the sedimentaries and also in the limestone
The stream
t i n was manifestly d e rived from the t in bearing veins and rock
and con c entrated in the gravels by the rive rs and their lateral
streams
I n many places th e gravels r e st on a fa ls e—bottom of s t i ff kaolin
derived from the disint e gra t ion of t he granite out c rops Th e y
vary from 1 t o 1 5 feet thick and are overla i n by an ov e rburden
ranging from 5 to 80 feet d ee p Th e richness of the grav e ls
varies from 5 1b to 4 0 lb p e r cub i c yard
The tin—stone of this reg i on is very pure generally containing
from 7 0 to 7 5 per c e nt of the metal
The colour is oft e n
black a n d sometimes pale brown or white The ore is found in
pi e ces of all sizes from fi n e sand to bould e rs half a ton in w ei ght
Th e associated m i nerals are magnetite and ilmen ite
The States of Perak Selangor N egri Sembilan Pahang and the
D utch E ast I n die s yi e ld two t hirds of th e world s produ c ti on of
ti n O i these the Sta t e of Perak produces about one th i rd and
3
the Sta t e of Selangor on e th i rd of the total output
The tin plac e rs in the Kinta V alley in the S tate of Perak
cov e r an ar e a 4 0 miles long and about 2 5 miles wid e and yi e ld
about three fourths of the tin—ston e raised in Perak I n 190 4
Perak produced
tons of t in
Oth er T in P l a cer s — There ar e stream tin mines in Burmah
S i am and China and in the Commonw e alth of Australia in th e
States of N ew South Wales Queensland V ictoria and Tasman i a
-
-
.
-
,
-
.
-
.
,
,
,
,
.
-
.
.
,
,
-
,
.
,
,
,
.
-
,
.
,
.
,
.
.
.
.
,
.
.
,
,
.
,
.
.
-
,
,
’
-
.
,
,
-
,
,
-
.
,
,
,
,
-
.
.
-
,
.
,
,
,
,
,
1
R A
.
2
3
.
F
Pe ro e
F O we
n
.
s
.
,
n,
P ro e
en
Z oe
.
s
,
Jr
.
J ou r n a l
ci t
.
M
i i g i Perak
n n
n
”
,
f
o
G
Fe b 1 903
eol ogy ,
T r a ns I
.
.
ns t
.
.
,
M in
.
.
a nd
M et
.
,
v ol .
vi
.
1
5
p
.
.
C LA S S IFI C AT I ON
MIN ERAL D EP O S I T S
or
21
.
The stream tin deposits of Co rn wall and Saxony have long b e en
-
l a tin u m P l a c e rs
P
p e r cen t of th e platinum of
commerc e i s found as loose grains in th e grav e ls of t h e r i vers
draining th e e astern slop e s of t h e Ural M oun tains The grav e ls
g e nerally con ta i n some a lluv i al gol d
A li tt l e plat i num has b e en found in situ in p e r i dot i te a n d
olivine gabbro bu t not i n pa yable quantity Ultra basic e rup t iv e s
and somet i me s chloritic a n d ta lcos e sch i sts pr e vail in th e ne i gh
b o u rh ood of t he pla t in u m plac e rs 5 and fragm e n t s of th e se rocks
pr e dominat e in the sands and gr av e ls t hereby i ndicat i ng pr e t ty
conclusiv e ly that t he noble me tal was derived from th e adj acen t
a r ea by the o rdina ry proc e sses of wea th e r ing and e rosion
The domestic supply of pla t inum
P l a tinu m in A m e ric a
in th e U nited S tates is obta ined from the gold place rs i n T rini ty
and Shasta counties California The gold drif ts in Colomb i a in
Sou t h Am e ri c a B raz i l Bri t ish Columbia and N ew Zealand also
yield a small quanti ty of the metal
Platinum is always alloyed with a small propo rtion of iridium
and oft e n with a smaller amount of osmium
P la tinu m in R u s s ia
N early
.
—
90
.
.
.
-
-
.
,
,
,
,
.
-
.
,
,
-
,
,
.
,
,
,
.
,
.
I
ro n s a n d
P la c e rs
.
E normous depos its of black iron sa n d mostly t i ta nif e rous exis t
on t he c oas t of Chili ; on th e nor t h shore of the S t Lawr e nce i n
Canada 5 on th e coa st of California 5 and in Ne w Zealand 0 11 t h e
,
,
,
,
coast between Taranaki and Wanganui
Th e s e ir ons a n d d e pos its wer e d e rived in mos t cas e s from
weath e red and denud e d later eruptive roc ks n e ar t he coas t l i n e
I n some parts of th e coasts of Cal iforn i a and Ne w Zea land t h e
black san ds con ta in payable gold
.
,
,
.
,
,
.
em
G
P la c e rs
.
D ia m o nd P l a c e rs — River d e posits yield diamonds ,
ubies
sapphires and other pre c ious stones The diamon ds of Braz i l
and N ew South Wal e s are obtained from gravels The diamond
place rs of the V aal River in Sou th Africa y ie ld gems of grea t
size and purity
—
l
The princ i pal ruby produ c ing region in
R u b y P a c e rs
Burma is situated near M ogok about 90 miles d u e north of
M andalay Th e r ubies are usually found in a somewhat tenacious
.
r
,
.
,
.
,
,
.
-
,
.
,
,
.
MINI N G G EOLOGY
22
.
clay or in material passing from fi n e gravel to r iver sa nd T h e
country rock is a v e ry hard gneiss passing in pla c es into gra n ite 5
l
or a soft friable mi c aceous s c h is t
The district of Chantabun in S iam has long be e n famous for
its ruby and sapphire min e s
S a p p h ire P l a c e rs — I a the sapphire fi e lds of A n akie in
Queensland the wash is often c layey and sometim e s friable and
free from clay I n these deposits are also found oth e r pre c ious
stones notably ruby diamond topaz peridot moonstone cat s
eye and cairngorm
.
,
,
.
,
,
.
.
,
,
,
.
’
,
,
,
,
,
,
.
,
b
s
i
M
s
v
e
a
( )
D eposits
.
of this class o cc ur as layers or sheets and irregular
masses lying on the surfa c e or cov e red with soils surfac e clays
e tc of rec e nt accumulation They include deposits of bog iron
ore and in some places those of manganese and rock phosphate
—
Bog iron generally occu rs as i rr egular
B og iro n D e p o s its
layers or l e nti c ular masses which were deposited in shallow lak e s
or swamps
The iron in the maj ority of c ases was d e rived from lodes or
deposits of iron in the adj a c ent country The decomposition of
iron bearing minerals has doubtless contributed its po rt ion of
iron E xtensive beds of bog iron are oft e n found near the o u t
crops of pyritic lodes and of beds of th e carbonate ore
When iron pyrites is oxidised a large portion of it passes into
salts soluble in water 5 while carbonate of iron is read i ly solubl e
i n wat e r containing dissolved carbonic acid
Atmospheric
w eath ering must therefore daily liberate a large amount of iron
in a soluble fo r m
I t is well known that wh e n chalybeate waters are e xposed in
shallow sheets as in ponds lagoo n s and swamps to the actio n of
the air the i ron is deposited as the carbonate Fr e sh ly pre
c i ita t e d iron may be fr e quently seen in s t agnant pools in swamps
p
The precipitation is caus e d by the action of atmospheric ca rbon
dioxide I n some cases the iron is thrown down as the hydrated
oxide by decomposing vegeta ble products
Bog iron ores are porous and cindery in structure They
contain in many cases too h i gh a propo rtion of phospho r us to be
useful for smelting pu rpos e s
—
Whe r e su pe r fic ial ore
A c tio n o f D e s c e n din g W a te rs
bodies have been fo rmed by the a c tion of descending wate rs i t
will be found as a ge n eral ru le that the waters have merely acted
,
,
,
,
.
,
,
-
.
,
-
,
,
-
.
-
.
,
.
,
,
.
-
,
,
-
.
,
.
.
,
,
.
,
,
.
,
,
,
,
.
,
.
.
.
-
,
.
,
,
.
.
,
,
,
1
T
Jll et
.
T
v ol
.
.
W y nn e
v.
“
,
1 897, p 1 6 1
.
b
T h e Ru y M
.
”
m h , T r a ns
i nes o f Bur a
.
I
ns t
.
M in
.
a nd
C LAS S IFI C AT I O N
OF
MIN ERAL D EP O S I T S
23
.
upon and concentrate d or e s d i ss e minat e d in th e adj a cent coun t ry
rock Such seconda ry c oncentra t ion i s often s ee n i n th e case of
i ron mangan e s e a n d phosphate d e pos i ts
A t ypical exampl e of t h i s class of or e body is the gr e a t deposi t
of limon ite at Parapara i n Ne w Z e alan d wh i ch occurs as an
irr egular shee t of or e ly i ng on t he surfac e in a d e pression form e d
in Pal aeozoic schis t The or i gi nal sourc e of the iron is t h e sch i st
and associated l i m e ston e
1
E xampl e s of th e same k i nd ar e foun d in P e nnsylvania
Th e
ores are larg e ly limoni t e Th e y occur as rounded or elonga t e d
fragments w i th r e sidual clay i n irr e gular d e pos i ts i n ca viti es
Th e source of th e iron is th e Pal aeozoic shales and lim e s tone in
which the primary iron is dis s e mina t ed in t he form of carbonate
sulph i de and silicate
.
,
,
.
-
,
.
.
.
.
.
,
,
,
FIG
.
l 2 — S e c tio n
Pe yl nia F rn c O b k h o wi g depo ition
o f li m o ite b y de e di g water i th b ddi g n d j oi t plane
d
od lar iro n o r i h o llo w i l i me tone ( A fter T C Hopki )
.
.
at
th e
n
sc
n
n
nns
n
s
e
n
s
n
n
es
u
a e
u
va
s
re -
an
n
e
,
n
s
n
a
.
.
s
s , an
ns
.
.
Th e mangan e se d e pos its of Cartersvill e in t he Sou t hern
Appal a chians of the Sta t e of G eorgia are among t h e most impo r t
ant in America They occur e mbedd e d i n a thick d e pos it of
res i dual clays ma i nly d e rived from t he d e cay of t h e Beav e r l i me
s ton e a n d Weis n e r quartz i tes of Cambrian age
2
Acco rd i ng t o T L Watson the ore is distribu te d irr e gularly
throughout t he clays in the form of pockets l e n t ic ul ar masses
veins and string e rs single nodules and concr et iona ry mas s e s 5 and
small diss e min ate d grai n s I n extreme cases the la rges t
as
poc k e ts may yi e ld as much as s e veral hundr e d to ns of or e Th e y
are rarely composed of so l i d ore t he usual form being t ha t of
nodules thickly studded through the clay
O i the mangan e se oxid e s wh i ch occur pyrolus it e and milom e la n e
,
.
.
.
.
,
,
,
,
.
.
,
.
,
1
C
2
L
I ns t M E
T
T
.
.
.
.
.
Hopki
W t on
ns,
a s
,
v ol
.
,
B
u
xxxi v
l letin G
T h e M an
.
S oc A m
an s Ore
e ol
1 90 4 , p
.
.
.
g ee
2 22
.
,
v ol
.
xi
.
p 4 75
.
.
Depos its o f Georgia
,
T r a ns A m
.
.
MINI N G GEOLOGY
24
.
greatly predominate Beds of limonite oc c ur separately or in
c lose asso c iation with the ma n ganes e ox i des forming mangan i f e rous
iron ores of varying grades of purity
The imme di at e sourc e of th e mangan e se is held by Watson and
others to b e rocks from which th e r e si dual clays enclos i ng th e or e s
w e re derived The dissolution and concentrat i on of the manganes e
was effe cted by desc e nding waters charged with oxygen carbon i c
and organic acids
I n th e Cav e Sprin g district in th e adj oining co u n ty th e
mangan e se ores are c on fin e d to r e sidual clays deriv e d from th e
Knox dolomit e stratigraphically h i gh e r than the quartzites a n d
limestones of Cartersville district M assiv e cherty beds occur in
.
,
.
.
,
.
,
,
.
8
FI G
.
e tio
eo gi
.
i e
.
fragme nts
resi dual cl ay
A
C,
O pe n in gs at th e D obbi n M i ne near Carte
o i g
o c c urrence f m n g ne e e in th re si du l
o Pe o se by Wat on )
m asse s o f parti lly decaye d ro ck ; B ma ng nes e o e
n in o n e o f t h e
13 — S c
v ll , G r a , s h w n th e
c lay s
( M odifie d fr m nr
,
.
a nd
s
o
s
a
a
s
al a n d
or
,
verti cal scale
a
e
.
a
Horizo nt
rs
,
,
1 in = 1 0 ft
.
a
r
.
the limestone in pla c es a n d the decay of the rocks in these pla c es
has formed manganiferous c hert breccias which howev e r are not
of much economic importance Th e following figure shows the
form of d e c ay assum e d by th e Knox limestone w h i ch is ascribed to
th e Silurian period
The important mangan e se or e s of Roman eche ( S a one e t L oire )
o c cur according to D e L aunay 1 bo th as ve i ns wh i ch traverse the
granite and as irregu lar shee t s in red clays intercalated in l i m e
stone Th e latter abut against a nearly v e rt i cal wall of grani t e
The verti c al boundary between the granit e and th e Secondary
1
Pro fes s or L de Lau nay Comp tes R endus v iii S ession Congr es G ol I n ter
n a tion
Paris 1 90 1 p 96 8
,
-
,
,
.
.
-
,
-
,
.
.
’
.
,
,
,
.
,
.
.
e
.
C LAS S IFI C A T I O N
MIN ERAL D EP O S I T S
or
25
.
rocks is occup ie d by a v e in of mangane s e Th es e d e pos it s app e ar
to b e pa rtly contac t or e s a n d pa rtly r e placem e nts of t h e lim e s ton e
Th e valuabl e i ron —deposits on th e M e s ab i rang e n e ar the nort h
shor e of L ak e S up e r i or are b e l ie ve d to b e du e to s e condary con
c e ntra ti on by t h e ac t ion of d e sc e nd i ng wa te r G reat bod i e s of
or e l ie on the su rfac e and pass und e r h e avy d e pos it s of glac i al
.
.
,
,
.
This sub—class also i nclud e s t h e
surfac e depos i ts of sal t i n Asia Am e rica a n d Aus t ral i a as w e ll as
t he valuable d e pos i ts at L ak e A l b e rt N yanza i n Af r i ca
B o ra x D e p o s its —A larg e proport ion of t h e borax of com
m e l e e i s obtained from muds a n d marsh s e dimen t s Th e muds of
D agg e t t P a con ta i n valuabl e d epos i ts of sodium bora te as also
Th e marsh e s of California and Ne vada also
do t hos e of Turk e y
y ie l d a small outpu t
S u p e rfi c ia l S a l t D e p o s it s
—
.
,
,
,
.
.
.
,
.
,
,
.
.
FI
G
.
e tion i K o x D o lo mite 2 m i le ea t o f Ki ng ton G eorgia
i ll tr ting de ay o f th m g e i n l im e tone by fl w o f undergro nd
water
( M d ifi d fro m S pen er by Wat o
A re i d l l y B
i
li
m
t
g
14 — S
.
us
n
c
.
o
e
e
,
s
,
c
a
s
n
n s a
a
s
ua
c a
,
n1a
,
,
u
o
s n
c
s
s
s
.
ne s a n
e s on e
.
—
G
D
o
Gypsum
e p s it s
S u p e rfi c ia l y p s u m
is fo u nd forming
thick b e ds on th e fl oor of crat e r lak e s i n volcan i c r e gions A
notable e xampl e of th i s i s seen at Whi t e I sland in N e w Z ealand
w h e r e th e banks a n d fl oor of t h e c r at e r lak e are cover e d with an
incrusta t i on of gypsum and sulphur many f ee t t h i ck
G ypsum al s o occu rs as b e ds associated with calcareous and
arg i llac e ous rocks ; a n d i n d i sseminate d crystals i n clays and
.
-
.
,
-
.
N ativ e sulphur occu rs most frequ e ntly
volcan i c r e gions ofte n a s soc i ated with sulphur and c e lest i n e
S u l p h u r D e p o s its
in
—
.
.
26
MININ G GEOLOGY
I t occurs
.
beds in the valleys of N ot e and M a z za ro in S icily 5 at
Solfata ra near N a ple s 5 also in J ava J apan and Ne w Z e aland
in
,
,
C L ASS
D EP O S I T S
( )
b
( )
( )
Con stitu ting B
D ip
—A
a
a nd
.
—S T R AT I F I ED
Cons titu ting beds or s tra ta
D issemin a te d th rou gh a be d
a
S t rik e
II
.
,
.
.
Of
B e ds
e ds or
S tr a ta
.
.
bed or seam is a member of a
s t ra tifi e d formation the overly i ng layer forming the roof and the
und e rlying the fl oor
The s tr ike of a bed or seam is the direction of a horizonta l line
drawn along the plane of the s tra tifi c a tion
The dip is the direction to wards which a bed inclines and is
always at right angles to the strike I f w e assume that we a re
standing upon the outcrop of a vein running or s t riking no rth
and south and facing north it will be found t hat the dip may b e
either to the right or left that is to the east or west
The dip or direction of th e in clin ation of a bed or v e in must not
be confounded with the inclination or a ng le of dip
T h e I n c l in a tio n O f B e dS — The a ng le of d ip is the do wn
wa r d inclination measured in degrees f rom the h or izon ta l
Th e u nder lie is the downward inclination measured in degr ees
from the v er tic a l
The dip and underlie a r e only the same when t he inc lination
,
,
.
.
,
.
,
,
,
.
,
,
.
~
.
.
.
F IG S
.
15
an d
16
.
— S h o w i n g I ncl ination o f V ei n s by Co o rdinates
-
.
of the bed or vein is
The te r m u nderlie is in common
use among miners and is apt to le ad to confusion if used care
lessly
When des c ribing a bed or seam a geologist will gene rally say
The seam strikes north south and d i ps east at an angle of
This means that the dire c tion towards which the seam in c lines is
,
.
,
-
,
28
MININ G GEO L O G Y
.
yea rs however have shown that coal oc c u rs in rock of all ages ;
and the invest i ga t ion of the newer coal measures has led to the
belief that c oal vegetation established itself wherever and when
ever the conditions were favourable for its growth
I n tra c ing th e success i on of pl an t a n d animal l i fe i n geological
time i t is found that the e arlier fo rms wer e of a v e ry prim i tiv e
type I n asc e nding the g e olog i cal scale t hese earl ie r forms wer e
su c ceed e d and to a large e xt e nt displaced by more highly
organis e d forms doubtless better adapted to th e prevailing con
dition s of th e time and pla c e
I n resp e c t to plant life the Primary period was specially
distinguished by the great developm e nt of mosses ferns and
o ther cryptogamic forms 5 the S econdary period by th e growth of
cycads and fe rns 5 and the Tertiary by deciduous trees and
fl o we r in g plants
The coals of the di fferent geological periods are formed of th e
veg e tation prevailing at that time Henc e th e Carbonif e rous
coals of E urop e are compos e d of the r e mains of f e rns mosses
equisetums lycopodiums and l e pidodendrons many of which
grew to a gigan ti c s i ze resembl i ng i n their habit the forest tr e es
of the pr e sent time
The gr e at c oald e pos its of Carboniferous age would indicat e
that plant life in this period reached its maximum developm e nt
at taining a luxuriance unrivalled at any later geological period
Ther e is good reason for the belief that the coal —vegetation of
this and all later periods grew 0 11 wide tra c ts of low lying swampy
1a n d a dj a c e n t to some sea or lake e nv e loped in a cloud of s te am
ing vapour th rough which th e rays of the sun s e ldom p e n e trated
M any of these an c ient forests extended for hundreds of miles
occ u py i ng the estuaries and deltas of great slugg i sh riv e rs laden
with mud and fi n e sediments
A study of the coal measures of eve ry count ry and of e v e ry
age reveals the fact that the accumulated coal vegeta t ion was
preserved from des t ruction by the gradual submergence of th e
land whi c h t hus permitted the deposition of a great thickn e ss of
protecting sedimen t s
The succession of seams met with in many c oa lfi e lds indicates
successive p e riods of minor subsidence and elevation of the land
e ach seam with its underclay marking the site of a n e w forest
The thickn e ss of the beds or strata b e tween the diffe rent seams
a ff ords some evidence of the extent and duration of e ach sub
m e rgence 5 b u t th e clay partings met with in coal seams cannot
always be taken as an eviden c e of submergen c e They may mark
an encroachment of fi ood waters on to the forests dur i ng an
abnormal inundation whereby a layer of mud was d e posited
,
,
-
-
.
,
,
.
,
,
,
.
-
,
,
,
.
.
,
,
,
,
,
,
.
-
,
.
-
,
,
,
.
.
,
,
.
-
-
,
.
,
.
-
.
-
,
C LA S S IFI C AT I O N
MIN ERAL D EP O S IT S
or
29
.
among t he v e getation whose growth would be reta rded but not
,
,
charac t er of t h e sed iments
su cc eeding th e coa l na t urally var i ed wi t h the position of t he
fores t s and t h ei r prox i mity t o th e s e a e ven for coal s of th e
sam e age
Subsidence of t h e land was a fundamenta l requir e m e n t for the
pres e rvat i on of t he accumulate d coa l vegeta tion I n most coun t rie s
t h e coal 18 follo wed by shales or indurated clays sandstones a n d
l i mes t ones
Th e shales are commo nl y forme d of fi u v ia t ile mu ds which
generally contain plant—r e ma i ns 5 th e sands t on e s ar e fi u v io mar i n e
and often conta in a rich mollusc an faun a ; wh i l e the l i m e s t on e s
ar e compo s e d of shells and co rals which ind i ca t e a t ru e mar i n e
l i t toral I n th e se cas es the c oal m arks th e beginning of a cycl e of
deposit i on
Wher e the coal —v e geta ti on gr e w on the marg i ns of lak e s or in
lake estua ries the coal measures cons i st principally of shal e s gr its
and sandston e s I n most plac e s th e gr i t s i m de rlie t h e coal
—
C
o
Carbon a ceo us ma t ter i s found in rocks of all
A g e of
al
ag e s and in nearly all kinds of sedim e nta ry rocks
T h e graphite be d s of Canada oc cur in rocks of La uren ti an ag e
Th e an th ra cite of Coun ty Cavan i n I reland i s S i lurian 5 the gr e a t
c oa lfi e l ds of G r e at Bri t a i n Con ti n e n ta l E urope a n d United S ta t es
ar e Carboniferous 5 the c oals of Ne w S out h Wales S ta t e of
Vi rgin i a I ndia and Ch i na Carboniferous and Fe rmo—c arbon i f e rous 5
the bi t um i no u s coals of N ew Z e aland Upp e r Cr eta c eous 5 th e
brown coals of Sou t h Hungary Pennsylvania and N or t h G ermany
O oli t ic and L iassic ; of N e w Zealand and V ienna bas in M iocene 5
a n d t h e l i gn i te beds of I r e land Pl i oc ene
Th e coal measur es wi t h
I n c l i n e d P o s itio n o f Co a l S e a m s
th ei r accompanying seams of coal w e r e ori ginally d e po s it ed in a
mor e or less horizontal posit i on I f the stra t a had r e mained
horizon tal i t is ev i dent t hat the task of procur i ng coal would hav e
been v e ry labo rious and expensive 5 a n d in coun t r ie s where th e
overlying strata are t h i ck th e coal co u ld no t have b ee n reach ed
The s e cular movem e n t s of th e cru s t of t h e e a rt h have t il ted the
s t ra ta a t different angles th e dip varying from a few degr e es to
a n gl e s wh i ch occasionally approach the vertical
F a u l ting O f C o a l S e a m s — Sudd e n dislocations or changes of
po s iti on ar e spoken of as th r ows tr ou bles slip s or fa u lts
I n coal stra ta faults often occur in a ser i es of two or mor e
hav i ng a parall e l b e aring Th ey som e ti m e s all d i p one way bu t
fr e quen tly in oppo s ite d i r e ctions
S tep f a u lts are of t en me t w it h i n coal m e asures
Wher e t h e
M o de
O c c u rre n c e
Of
.
—T h e
,
.
-
.
,
,
,
.
,
-
,
,
.
.
-
,
,
.
,
.
.
.
,
.
,
,
,
,
,
,
,
,
,
,
,
,
,
,
.
-
-
,
.
,
.
,
.
,
.
.
,
,
,
.
-
,
.
,
.
-
-
.
30
MINI N
G EOLOGY
G
.
dislo c ations do not exce e d the thi c kness of the c oal seam they are
t erm e d h itch es
—
F ault lin e s are ofte n so thin as to be
E x te nt O f F a u lts
e asily mistaken for th e ordinary j ointing of th e beds which they
traverse M or e frequen t ly how e ver t he opposi t e faces pr e sent
smooth glassy slicken sided walls with a space partially or
entirely fi lle d with clay or debr is derived from the adj oining
rocks
I n many c ases the faulting has been caused by lodes or c ross
courses which often con t ain threads or pock ets of iron pyr i tes
known to c oal miners as bra ss es 5 and where they interse c t a coal
seam quantities of sooty coal mix e d with clay
—
D ykes consist of
I n t ru s iv e D y k e s a n d th e ir E ffe c ts
wall l i ke masses of igneous rock often basaltic
They are
vert i cal or incl i n e d at various angl e s and sometimes a c t the part
of faults by d i splacing the strata on the O pposite walls They
sometimes run parallel to faults
I n t he c oal fie lds of Scotland sheets of basalt h a ve been forced
along the surfaces of coal seams and even along thei r centre so as
t o form a bed or sheet in the middle of the seam
I ntrusive dykes and sh e ets or sills sometimes c ause great loss of
coal and extra e xpense in the working of the seam
The coal in the vi c in ity of an igneous mass is often coked and
rend e red c inde ry or sooty
But t he e ff ects ar e not always destructive A t M alvern Hills in
N ew Zealand a sea m of brown coal was dehydrat e d and conve rted
into anthracite of good quality by a sheet of basalt
Coal may also be alter e d by the same agency into graphite
Among the debris on the slopes of M ount E gmont in N ew Zealand
80
0
0
a
beaut
i
ful
volcanic
on
e
which
is
piled
up
to
a
h
e
ight
of
c
(
feet upon a fl oor of th e lower Tertiary brown coal measures )
masses of sandstone with adhering layers of graphite of fi n e
quality are of not un common occurr e nce
I g n eous dyk e s oft en dam back water in coal mines 5 and i n
some cases they ha v e e ff e ctually pr e vented the spread of fi r e
I rre g u l a rit ie s o f Co a l S e a m s —The troubles m e t with in
coal min i ng are known as ba l/cs mp s g a ws s a ddle ba c hs s wellies
o
t
t
b
o
t
o
m
s
h
o
rse
s
and s h a ken coa l
p
B a lhs are sudden thinnings in the coal occas i oned by a
depression of the roof of the seam accompanied by a correspond
ing rising of the fl oor
Wh e n the stratum above the coal invades the thickness of the
seam so as to almost or entirely take the place of the coal it is
called a h ip or wa nt
G a me and s a dd le ba c/cs appear to be the reverse of nips as th e
-
.
-
.
,
.
,
-
,
,
,
.
-
,
,
-
,
.
,
-
.
,
,
,
.
.
-
,
,
.
.
,
,
.
,
.
,
.
.
,
-
,
.
-
.
.
’
-
-
,
,
,
,
,
‘
-
,
,
.
,
,
.
,
,
.
-
,
C LAS S I FI C AT I O N
MIN E RAL D E P O S I T S
or
31
.
is e ith e r irregu lar or ris e s into and inte rfer e s with th e
—
con t inuity of th e e oa l s e am
I n s wellies and p ot bu ttoms the ordinary th i ckness of th e c oal is
increased by a depress i on of th e fl oo r
Coal sea ms which r e s t clos e to the b asement rock are always
the mos t subj e ct t o irregul ari ti e s i n th i ckness Th i s i s a v e ry
no ti c e able f e a t ure of t h e Auckland coa lfi e lds of N ew Zealand
wher e the s e ams of brown coa l c onform to some e x ten t to the
conto ur of the bas e m e nt roc k T h e r e sult o f t h i s conform ity i s
tha t t h e coal thins where the b as ement rock ris e s in ri dg e s and
t hick e ns in the b e llows I n t h e depressio ns t he s e am i s som e
ti m e s 60 feet thick and on the ridges only a few f eet T h e t hick
e n in
and
t
hin
ing
of
the
seam
does
not
n
e
ces
s
ar
i
ly
i
mply
t
ha
t
n
g
t he coal is de t r ital for i t is manifes t tha t t he w et spongy p e aty
mass of vege tabl e matter from wh i ch th e coal was form e d would
slowly gravitate towa rds and ac cumu lat e in the hollows ex i sting in
th e land s u rface 0 11 which th e vegetat i on grew
S h a ken coa l is coal wh i c h app ea rs to hav e b e en compl etely
cr ush e d by some pressure or movement of t h e stra ta
It i s
oft en a mere h e ap of shapeless coal dus t which i s so soft t ha t it
may be du g ou t w i th a spa de
—
B e n din g O f C o a l S e a m s T h e effec t of fa u l ts 1 o lc a n ic
in t rusions or late ral pr e ssur e due to the con t raction of the crus t
of th e ea rth has b e en some t imes to bend the coal strata and in
some c a s e s t hrow t hem into complica te d folds which i ncrease the
cos t of working and ca use a g reat was te of coal i n mining
E xamples of t he f olding of t h e s t rata i n th e anthrac i te c oa lfie lds
of Pen nsylvania are sho wn in the fig s 1 8 and 19
fl oo r
.
-
.
-
.
,
.
,
.
.
,
,
,
,
,
.
.
-
,
.
'
,
.
,
,
,
,
.
FIG
.
e tio o f N w Bo to n B in Penn y lva i a th racite
region ( Red ed b y B S Ly man fro m th cro ection h e t f th
Pe ylv ia G eo l ogi l S rvey
18 —
.
C ro
.
ss s c
e
uc
.
nn s
n
.
an
ca
s
,
e
.
u
as
s
ss -s
n a
s
n
e
o
e
.
I n fig 19 w e have an i nst r uctive exampl e of i nverte d folding on
th e sam e c oal fie lds
The compli c ated manner in which coa l me asur e s are fold e d i s
.
.
-
32
MININ G GEOLOGY
.
well illustrated in the c oal—bas in of S aint E loy in F rance
l
typi cal section of this fi e ld drawn by D e L a u n ay i s sho wn in fi g
A
.
,
FI G
.
19 —
sh w n
,
.
20
Cro ec tio S h
d h B i n Pen y l n i an th r c ite regio
o i g i verted foldi g f o l m ea re ( Red ed by B S Lym
fro m cro ect ion h eet o f th Pe n y lvan i Geol ogi l S rvey )
s s -s
.
n
n
s s -s
FI G
.
n
c
o
c
C oal
as
n
al
B
as i n
I
a nd
,
ns
,
-
a
e
e tion o f Co
of
Va rie tie s
a
s
20 — S
.
e n an
su
va
uc
s.
s
i nt El o y
u
.
( A fter D e L au n a y )
.
n flu e nc e o f
n,
an
.
.
ca
a
Sa
a
a
.
.
E n c lo s ing R o c k
.
Assuming c oal to b e a form of altered v e ge table mat te r th e pro
m
a re indicat e d by th e following
t
stages
in
its
for
a
ion
i
r
e
s
s
v
e
g
kinds
P
e
at
1
( )
L
i
gnite
2
( )
Brown
coal
3
( )
Cann
e
l
coa
l
4
( )
B
i
tuminous
or
caking
coal
5
( )
—
Semi
anthracite
smokeless
oal
6
c
( )
Anthracit
e
7
( )
The quality of a coal is not so much dependent upon the age of
the coal as upon the thi ckness an d li tholog i cal character of the coal
measures A gr e at thickness of close grained imp e rv i ous strata
e nabl e s the alteration of the vegetabl e matter to proceed without
,
.
.
.
’
-
.
.
-
.
.
-
.
1
I
Pro fe o
ss
r
n ter n a tio na l ,
L
de
.
P ri
a
s,
L au nay
Comp tes R eh du s , m iz
1 90 1 , p 959
.
’
’
’
.
,
.
S essi on
Congr eh G
eol
.
C LA S S IFI C A T I O N
MIN ERAL D EP O S I T S
OF
33
.
a c cess of air or water thereby produ c ing c oals of high quali ty
w i thout regard to age
Th e fi n e b i tuminous s t eam coals of the w e st coast of N ew Zea
lan d of Upper Creta c eous age are en c losed in a gr e at th i ckness
of close gra i ne d sandstones and shales Th e coals of the sam e age
on t h e e as t coa st ar e enclosed in po rous qua rtz gri t s and are lit t le
be tte r than l i gn i t e
Another example of th e in fl u e n c e e x e rcised by the enclos ing
rocks upon t h e character of the coal is seen in t h e c oa lfie lds of
1
e ast e r n T e xas I n the F aye t te Y e gua and T i mb e r Bel t d i vis i ons
wh e r e th e e nclosing rocks are c h ie fl y soft sandy clays and shales
t h e coa l i s only a l i gnite w h il e in Webb County wh e r e th e m e asur e s
are san dstones and shales it i s so superior as to b e classed by
P e nros e i n the bituminous group of c oa ls
-
,
.
-
,
,
-
.
,
.
.
,
,
,
,
,
,
,
,
.
b
i
m
t
ed th r ou g h
D
sse
i
n
a
( )
a
B
ed
.
Sed i men tary rocks conta i ning well de fin e d horizons impregnated
wi t h or e s and m i n e rals of greater or l e ss econom i c value ar e found
i n many parts of t he glob e The origin of the metall i c con te n t s
of t hese b e ds i s a problem not yet sa tisfacto ri ly d eterm i ned Th e
metals wer e e i ther introduced contemporaneously wi t h the d e pos i
t ion of the sedim e n ts in which th e y oc cur or after t h e consol i da
t ion an d elevat i on of th e sediments above water The subj ec t
awaits furth e r investigation A fe w typ i cal examples of th i s class
of d e posit are given below
—
I n this class may b e inclu d e d t h e
B
k
T h e R a n d a n e t R e e fs
c e l e brated so ca lled ba nket or almond re e fs of the W i twate rsran d
in th e Transvaal
2
Th e bas emen t rock is granite wh i ch is intruded by dyk e s of
felsit e syen i te granuli t e e tc The grani t e is ov e rla i n by th e
Quartzite shal e group which consists of a gr e at th i ckness of
qua rt z ite and ferrug i nous shales dipp i ng south at angl e s varying
This gr oup wraps round th e no rt h s i d e
f rom 2 0 to
of J oh a n n e s b u r g I t conta i ns s e veral t h i n conglomerate or banke t
beds which are gol d bearing
The Quar t zi t e shale group is follow e d appar e ntly c om for m a b ly
by the W i t wate rsran d group — th e gold bea ring series prop e r
con sis ti ng principally of quart zites w i th which ar e associa te d beds
of conglome rate or bank e t sandstones and shales The d i p i s
south a t som e wha t lower angles t han th e und e rly i ng s e ri e s
Th e W it wa t ersrand group is overlain by an enormous pil e of
amygdaloidal diabase in its turn followe d by t h e Black Re e f
1 H i ri
S cran to n P
O c t 1 905 p 1 0 4
n c h R ie s M in es a nd M i ne ra ls
2
S J T ru sc ott T he Wztzoa te rs ra nd G oldfi e lds 18 98 p 1 8
-
.
.
,
.
.
.
.
-
,
,
,
.
,
,
,
,
-
.
,
,
,
°
.
-
.
,
-
,
,
-
,
.
,
.
,
,
e
,
,
,
a
.
.
,
,
’
.
,
,
,
.
.
.
.
34
MININ G GEOLOGY
.
formation
The latte r consists of alternating quartzites and
shale 5 and at its bas e conta i ns conglomerates of the banket type
varying from a few inches to 14 feet thick I t is separated from
the diabase by a few inch e s of ferruginous clay
The bulk of the gold in the Ba nd is der i ved from the M ain
Reef series i n the Witwate rsrand group which comprises three
important banket reefs namely
”
.
,
,
.
.
,
,
,
The
M
ain
Reef
the
lowest
)
(
( )
6
The
M
ain
Reef
L
eader
( )
The
outh
Reef
c
S
( )
a
.
.
.
I n addition to these th e re a re the less important bankets k n o wn
as the N orth Reef the M iddl e R e ef and the Bastard South Reefs
,
,
.
,
,
f
FIG
(1
an d
M i ddle R e
— C ro ss
6
7
e tio a ro s R obi on Mine ( A fter G ib on )
2 ) B tard S o th Ree f ; ( 3 ) D i b e D y ke ; ( 4 ) S o th R ee f ;
ef ; ( 6 ) Mai Ree f Leader ( 7 ) Mai Reef ; ( 8) N orth Ree f
.
21
.
-s
c
n
c
a
s
u
as
ns
s
s
.
as
u
n
n
.
(5 )
.
The banket be ds consist of pyrit i c quartz conglomerates composed
of rounded or sub angular p e bbles of bluish gr ay quartz embedded
in a quartzose matrix
Th e M a i n Reef series comprises three more or less payable r ee fs
or bank e t beds —namely the M ain Re e f which i s often 12 feet
thick and very low grad e 5 the M ain Reef L ead er about 1 5
in c hes thick and very rich ; and the South Reef varying fro m
a few inches to 6 feet thick and payable in mos t places This
series can b e traced for 4 6 miles and is the main sourc e of the
gold produc e d in th e Transvaal
A charac te r i s t ic f e ature of th e bankets is their uniform value
The e ven d is t r i bution of the gold has b e en a n i m portant factor
in th e d evelopm e nt of th e Rand g oldfie ld T h e gold does n ot
occur in t h e enclos e d p e bbles but i n t he cem e nt i ng med i um — a
circumstance wh i ch t e nds t o sho w that th e conglom e rates are
simply consol i da t ed lacustrin e or e stuar i ne d eposits in which the
gold was deposi t ed from circulating gol d b e aring solutions
—
M a n s fe l d C o p p e r S h a l e s
The copp e r bear i ng shales ( Kup
f e r s c h ie fe r ) of M ansfel d in Prussian Saxony are of Perm i an age
They are 18 inches thick and extend for many m i les I n places
,
-
-
,
.
,
,
,
,
,
,
,
.
,
.
.
.
,
-
.
-
.
,
,
,
.
.
36
MININ G GEOLOGY
.
E urope They consist of alternating shales and sa ndstones of
Triass i c age
.
.
The White Reef and Bu c k eye Reef a re two sandstone beds
from 30 0 0 fe e t to 4 0 00 feet apart Above water l e vel they are
impr e gnated with ke ra rg y r ite or horn silv e r 5 and b e low water
l e vel the chloride is r e placed by sulphid e s The m e tal bear i n g
rock vari e s from 30 t o 90 feet wid e and yi e lds an av e rage of 2 5 o z
of silve r per ton A small percentage of copper also occurs with
the s i lver
Ne arly all geologists are agreed that the silver and c opper wer e
introduced subsequently to the tilting of the beds
—
L e a d S a n ds t o n e o f P r u s s ia
The lead sandstone of
C om m e rn in Rhen i sh Prussia is bel i eved to b e lower Triassic in
age The rock is a white sandstone of great thickness The
u pper part is charged w i th small concretions varying from a pin
h e ad to a pea i n size composed of quartzos e san d cemented with
galena
The con c retions are called knots h e nce th e min e rs nam e
They contain a little chromium vanadium
kn otten s a nds te in
and titanium 5 th e latter in t he greatest proportion Th e or e is
mine d partly by open cast and par t ly by underground workings
L e ad bearin g sedimentary rocks belonging to this class o c cur in
s e veral parts of G ermany and in the counti e s of N ottin g h a m and
L e i c e stershire in E ngland
—
B e ds c o nt a in ing C o p ro lite s Coprolites are found d i s
s e m i nat e d in greensands interbedded with strata of younger
Secondary ag e in t he south of E ngland
The coprolite b e aring
gr e ensands of t h e Cr e tac e ous Wa i para s e r ie s of N ew Z e al and are
of too low a grade to be of econom i c value
—
G y p s u m B e dS
Gypsum occurs in beds associated with
calcareous and clayey rocks I t is found in great quantity in the
Paris basin at M ontmartre I ts occurrenc e in vol canic reg i ons has
already been noted
-
,
-
.
,
-
.
,
.
.
.
.
.
,
,
,
.
.
,
.
,
,
.
’
,
-
,
,
.
,
.
-
.
-
,
.
,
.
.
.
.
.
.
.
C L ASS
II I — U N S T R AT I F I ED
.
D EP O S IT S
t
s of vol c a n ic or ig in
os
i
D
e
p
( )
t
ockwor k d ep os its
6
S
( )
0 ) Con ta c t a nd r ep la c em en t dep osi ts
(
h
l
b
a nd s
d
F
a
( )
e ) I mp r eg n a tion s
(
S eg r eg a te d veins
G a sh v e ins
T
e fi s su r e v eins
w
h
( )
a
.
.
.
.
.
.
.
.
.
C LA S S IFI C AT I O N
( )
a
M IN ERAL D EP O S I T S
or
D ep os its
n
r ig i n
o
l
i
c
O
ca
V
f
o
37
.
.
These includ e the de posi t s of sul phur and borax which
accumulate in and ar ound fumarol e s i n th e form of sublima tes
N ota ble exampl e s of sulphu r d e posits ar e found at M oun t Et na
and M ount V e suvius 5 Whi te I sland and Ro torua i n N e w
Zealand ; and m J apan
A t Whi te I sland t h e bulk of t h e sulphur is of ve ry low grad e
being m ix e d wi t h a v e ry larg e p ropo rt ion of gyp sum A t Roto rua
t housands of tons of bo th y e llow a n d black sul phur of high grad e
ar e be ing mined by t he natives for export
T h e steam fumarol e s of Pisa and G ros e t to in Italy yi e ld a
large a n nual ou t put of bo ric a cid
,
.
-
,
,
,
.
.
,
,
.
b
t
S
o
ckwor k D e osits
( )
p
.
The term stoc kwork was firs t used in E urope to dis t in gu ish
the quarry method of min i ng cer tain min e ralis e d rock mass e s
in terse c ted by small re t icul a ti ng v e inl e ts of or e I t no long e r
refe rs to t h e m e thod of working bu t is appli e d to m e ta ll if e rous
ore—bodies possessing t he characteristi cs of t h e d e pos i ts fi rs t mined
as stoc kworks
A stoc kwork may b e de fin e d as a r ock mass t rav e rs e d by
numerous small veins of or e t hat mu tually in te rs ec t e ach o t h e r
bu t ar e too small to be worked s e parately
Th e v e ins seldom poss e ss cl ea rly de fi n e d walls b u t merg e
impercep t ibly into t he coun t ry rock wh i ch i t s e lf is often
impregna t ed w it h min e ral matt er to a gr ea ter or less e x t ent
Stockworks are sometim e s of grea t wid t h and length They
ar e mostly of low grad e 5 a n d from n e cessi ty ar e commonl y worked
by t h e quarry or open cut system of minin g which enabl e s a larg e
output of ore to be produced at a small cos t
—
Th e c e l e bra t ed gold
A l as k a T r e a dw e ll S t o c k w o rk s
bearing ore bodi e s in t he Treadw e ll m i nes D ouglas I slan d in
1
Alaska acco rd i ng to Sp e nc e r c ons i s t of min e ral i s e d dyk e s of
alb i te dior i t e lyi ng b et w e en gr ee ns ton e on t h e hang i ng wall and
sla t e 0 11 th e foo t—wall wi t h a few small e r dyk e s nea r by i n t h e
slate Th e y g e nerally conform to t h e s t r i ke and dip of t h e
-
-
.
,
.
-
,
.
,
.
.
-
,
.
~
.
-
,
,
,
,
-
-
,
.
The greenston e s ar e as a rul e gr eatly al te r e d and in plac e s
possess a schistos e or slaty s t ruc t ure Th e y ar e suppos e d to be
ancien t an desites and basal t s that w e r e e rupted a t t h e t i me the
slates wer e form ed
1
A
C S pe n c e 1
T h e G eo l ogy o f t h e T rea dwell O re D epos its D o u g l as
I sl and A laska T r a ns A m I nst M E Pam phl et 190 4
,
,
,
.
.
.
.
,
,
,
,
.
.
.
.
.
,
.
38
MININ G GEOLOGY
.
The ore mainly consists of alt e r e d d iorit e impr e gnat e d with
sulphides c h ie fl y iron pyrites Th e rock is also partly shat t er e d
and fille d wi th a n e twork of thin calci t e and quar t z veins t hat
1
carry a fair proportion of sulphides
The dyk e s are considerably
mineralised and often th e whol e mass can be min e d I n general
the best ore is that wh i ch conta ins the gr e atest numb e r of calci te
and quartz veinle t s
The gold is associ
T h e gangue is felspar calcite and qua rtz
ated with about 2 per cent of pyr i tes and some magnetite
Pyrrho t ite often accompanies or replaces the pyrites
The ore is of very low grad e av e raging about twelve shillings
per ton but t he larg e ou t put free milling character of the ore
and skilful managemen t hav e enabl e d th e min e s t o pay handsome
odies are mined pa rtly by O pen
r o fits for many years
The
ore
b
p
cuts and partly by underground workings
O th e r S t o c k w o rk s — A t Zinnwald in Bohemia in a dome
shap e d mass of greisen (quartz and mica ) there ar e narrow hori
z e n ta l v e ins of tin or e that form stockworks
A t Altenberg ther e is a greisen like rock locally called Zwitter
in which t in ore is disseminated to th e ext e n t of one third to on e
half per cent thus forming a s tockwork S omewhat similar
deposits occur in granite in the form of impregnations
N ear S tanthorp e in Qu ee nsland grains of tin ar e d i ss e minated
through a gran i t i c rock as if forming on e of its original consti t uents
A t M ont e Catini in Tuscany t he Cr e tac e ous strata are broken
through by s e rpentine and gabbro containing large pockets of
coppe r or e mostly erub e scit e and copp e r pyrit e s
I n Cuba and N e wfou n dlan d rich d e posi t s of copper oc c ur in
s e rpentine
I n Cornwall granit e s and s laty shal e s locally call e d killas
containing from 8 lbs to 9 lbs of t i n stu ff to the t e n of rock yield
a good p rofi t I n some cas e s 2 lbs of t i n stu ff have been s u ffi c ie n t
to pay all exp e nses A man can br e ak from 15 to 2 tons of the
hard rock per day and 7 to 8 tons of soft killas
I n the mineral belt n e ar Ne lson in Ne w Z e aland native copper
d cuprit e occur in serp e ntin e and chromite of iron in massive
olivine
A t Kimb e rl e y in South Africa diamonds are foun d diss e m i
mat e d in tu fi s and agglomera t es oc c upyi n g the necks of ancient
volcano e s
.
,
.
,
.
.
.
,
,
.
.
,
,
.
,
-
,
,
,
-
.
.
,
.
,
,
,
-
.
-
,
,
-
-
.
.
,
.
,
,
,
.
,
,
,
,
.
.
,
,
.
.
,
.
.
.
,
.
,
,
,
.
,
,
’
.
( )
A contact deposit is on e which occurs a t or near
a sedimentary rock and an intrusive mass or dyke
1
A 0 S pe n cer loo cit p 2 5
c
Con ta c t
a nd
R ep la ce me n t D ep os its
.
-
,
.
.
.
,
.
.
,
.
.
,
th e
conta c t of
C L A S S IFI C A T I O N
MIN ERAL D EP O S I T S
OF
39
.
Valuabl e deposits of magn etite sp e cular iron and of copp e r
l e ad and zinc sulph ides are not uncommon along t h e j un ction
b e tw e en th e in t r usiv e and country rock frequ e n tly ne a r t h e
bounda ry but ne ver ou tside t he meta morp h os ed zone
I n most probably in all cas e s t he or e body i s a min e ralise d
replacement of the country rock followin g ce rta i n w e lld e fin e d
zones of fracture or c rush which are gene t ically conn e c te d wi t h
the igneous intrusive mass P e trolo g ica l m e thods of exam i na ti on
,
,
,
,
-
,
,
.
-
,
,
-
.
{4
F1G
22 — S
.
.
( a ) Gran ite
.
4
e tion ho wing Cont t D ep it
( b) S late
( ) C o tac t Depo its
c
ac
s
0
.
os
n
.
s
.
have shown that progr e ssive stag e s of al t era t ion ca n be t raced
from th e unal ter e d roc k to th e m i n e ra l is ed or e body
Th e al terat i on removal and r e plac e m e n t wer e du e t o as cend i ng
highl y h e ated wa te rs laden with min e ral ma tter d e riv e d from a
d e eper zone probably t h e cool i ng intrus i v e rock magma its e lf
Valuabl e de po si ts of m a gnetit e are found a t t h e con ta c t of im
pur e limesto n es and granite i n th e Chris t ian i a dis t rict, in N e rway
N ear F ramont in th e V osges in F ranc e m ass e s of sp e cular
iron a re fo u nd wrapping round a boss of qua rt z porphy ry
-B o
—
n
t
i
o
T
i
R
o
a
er
n
t
C
o
a
c
t
C
O i pyri ti c
i
i
re
d
s
P y r it c O
e
pp
contac t deposi ts t h e most typical in E urope ar e t hos e of Rio
T into Tha rsis a n d San D om i ngo i n Spain and adjace n t pa rt of
Portugal which occur at t h e boun dary be tw e en al te red sla t e and
fe lspar po rphyry
Th e famous coppe r min e s of Rio Tinto ar e con ta in ed in a g r ea t
b e l t of mineralised coun t ry 1 4 0 mil e s long and 30 m il e s w i d e
s t r e tchin g from Hu e lva i n Spa i n i nto Por tugal Th e co u nt ry is
slat e of Upp e r D e von i an ag e often loca lly al te r e d i n to jasp e r
talc —schis t a n d chias tol ite sch i s t and i n t ru de d by great mass e s of
quartz and f e lspar porphyry d i abas e quart z s yeni te and gran it e
Th e ore i s a fi n e grain e d and compac t i ron pyri t es con tain i ng
on an average less t han 3 p e r cen t of copp e r Small v ei ns of
copp e r pyri t es e r ub e sc i te and oc cas i onally copper glance mor e or
l e ss mixed w it h iron py rit e s qua rtz blende and oth e r m i nerals
trave rse t he m ass
-
.
,
,
-
,
.
,
.
,
,
,
-
.
.
.
-
,
,
,
,
,
-
.
,
,
,
,
.
,
,
,
,
-
-
,
.
,
-
,
.
.
,
,
,
,
.
,
,
,
40
MININ G GEOLOG Y
.
Conta c t Or es tn A mer ic a —
The argentif e rous lead ores of L ead
1
ville in Colorado hav e be e n describ e d by E mmons as contact
deposits occurri n g along th e contact planes of eruptive po rp h yry
dykes which hav e brok e n into and ov e rlain a b e d of dolomiti c
limestone
,
,
‘
,
.
1
( )
5
F I G 2 3 — S ectio n o f Rio T into Pyritic Contact D epo s it
Altered s late
( c) C u pri fero us py rites
( b) F el par porph yry
.
.
.
a
L
-
s
.
.
.
The lead zine ores of S outh M ountain in the S tate of I daho
occur along the c ontact of limestone and diorite or granite Th e y
2
have been described by L indg ren as true conta ct deposits
I n the S e v e n D evils distri c t in the same State there are coppe r
d e posits whi c h o cc u r as (a ) fi s su r e veins ( 6) zones of impregnation
and ( c ) c on tact deposits The country rocks consist of Triassic
slate and limestone intercalated with basic lavas I n s e veral
places this se ries is intruded by diorites ; and all the ore bea ring
bodies appea r to be gen e ti c ally connected with these int r usiv e
masses
The sedimentary se ries in di ff erent places has bee n fi ss u re d
in the zone of metamorphism and also outside of it The fi s s u re s
in the zone of metamorphism when fille d with mineral matter
formed contact deposits while those outside of it became fi ssu r e
veins M orphologically they di ff er but geneti c ally they are the
same
The valuabl e copper deposi t s of Arizona occur associa t ed w i th
Carboniferous limestone gen e rally at the line of contact of gran i te
or other erupt i ve rock
G old and copper bearing contact vei ns a re common in M exico
occurring generally between Creta c eous limeston e and eruptiv e
3
ro c ks which are nearly always diorite
-
,
,
.
-
.
,
,
-
,
,
-
-
.
.
,
-
.
,
,
.
,
,
,
,
-
,
,
.
.
,
,
.
-
-
,
,
.
o
e e i o f Certai
F Emm ns ,
T he G n s
v ol
1 2 5 , 1 886
,
, p
2
W L nd r n, T h e G n s s
T ra n s A m I n s t M in E ng V ol
1
S
M E
.
.
.
.
.
p 72 1
.
3
xv
i ge
.
.
.
“
.
.
.
e ei
.
.
.
.
,
.
L i n dgren
,
loc
.
c tt
.
,
4
2
7
p
.
.
s
n
O re
Depo s its
,
T r a ns A m I
.
.
n s t.
Ch ra ter o f Cert i Conta t Depo it
xxx i p 2 2 6 5 d G ene i o f O Depo it
and
a
.
.
a n
c
an
s s
c
re
s
s
s
”
.
s,
”
C LA S S IFI CAT I O N
MIN ERAL D E P O S I T S
0 11
41
.
Pyri ti c or e bodie s ass oc ia te d
D ep
with bu t not ac t ually in con tac t with e rup t iv e m ass e s ar e foun d
in all part s of t h e world
O f s u ch ore bodies tha t a t Ramm e l s
berg in th e Hart z sa id to have be e n worke d for 90 0 y e ars
M ount L y e ll lod es in Tasman i a and th e Broken H i ll lod e i n
N ew So ut h Wal e s may b e c ite d as typical e xampl e s
1
Vog t d e scribes th e Ramm e lsberg d e pos it as an irre g ular l e ns
of or e with a curious lateral b ranch l ik e th e Brok e n Hill lod e
The d e pos it is 1 5 00 yards long and from 4 9 to 6 5 fee t wid e It
i
R a n m els be rg
P y r itic
'
os it
—
-
,
,
,
”
-
.
,
,
,
‘
,
,
,
.
,
.
.
S E
24
.
—I deal S e c tion
o f Ra m m l
e s be r
é; Py riti Depo it
c
I S enclosed
s he a r
zo ne
s
.
( A fter
V ogt
.
)
in Upper D e vonian sla t es occupy ing t he cen tr e of a
It s gen e s i s is b e lieve d by V og t t o be closely
conn e c t ed w it h c e rta i n lin e s of erup ti on of grani te i n t h e
i mm e dia te n ei ghbourhood
—
t
a
l
os
i
Prof e ssor J W G r e gory group s
M o u n t L y e l Or e D ep
t he or e depos it s of t h i s di s t ric t i n to t wo class e s nam e ly ( a ) hug e
l e ns shaped pyr iti c mass e s a n d ( b) min e ral i sed ban ds of sch i s t
Pro fes s o r J H L V ogt U eber die Kies l ag ers tatte n v om T y p u s Reros
V ig s n as S u l itelm a in N orwege n u n d Ra mm el s berg in D eu ts chland
Z e tt
,
.
.
.
-
,
-
,
,
,
,
1
.
.
,
,
'
,
,
P
T
ra kt
2
.
G
e ol
.
,
Pro fe or
r a ns .
1 8 94
.
egory
J W G r
A us t I ns t A L E
ss
.
.
.
,
o t
,
v ol
.
x
.
e
T h e M u n Ly l l M
1 90 5 , p 2 6
,
.
.
ini g F ield—T
n
as
m an
.
ia
.
42
MININ G GEOLO G Y
.
forming fahlbands Th e form e r a r e t he sourc e of th e great bulk
of the valuable mineral m i ned in the fi e ld 5 t h e la t t e r ar e
economically of little importance
The rocks consist of D evon i an conglomerates and quartzites
flanked by Silurian and Cambrian sch i sts The structur e is not
complicated by folding but the c ountry is traversed by a compl e x
of great faults
The ore bodies occu r a s detached masses alo n g the line of
co n tact of th e quartzi t es and conglomerates on the east and
schists on the west side
O f the two main pyritic m asses the la rg e s t a n d most impo r tant
is known as the B ig M ine or P a rent M ine Professo r G rego ry
des c ribes it as irregula rly boat shaped in form be i n g an elliptical
mass which tapers gradually downwards and is th e n cut 0 11
with a rounded base T h e extension in depth is limited by a
great th r ust plane which brings the conglomerates under the ore
1
and schists
The oxid i sed gossan consisted mainly of silica ba r ite a n d iron
oxid e containing about 1 5 oz of silv e r and 1 5 dwt of gold p e r
t on
The pyritic ore is c h ie fly pyrites with coppe r gold and silv e r
Small patches of very rich or e probably the result of secondary
e nrichment were m e t with at the bottom of the oxidised zo n e
They contain e d redruthit e born ite fahlore and arg e n ti te
The main pyritic mass is of very low grade I t contains from
0 5 to 2 per c e nt of copper from 1 5 to 3 o z of silve r and
from 0 0 4 to 0 0 7 o z of gold per ton of ore
2
W T Bat c helor stat e s that a featur e of the or e bodies is their
p e cul i arity of splitting into on e or more legs or branches as they
d escend a feature so characteristic of the Broken Hill lode in
Ne w South Wales
The genesis of the M o u nt L yell ore bodies is still a question of
doubt Prof e ssor G r e go ry thinks they may be classed as contact
d e posits although not dir e ctly connected with igneous masses
Th e main or e body lies in a c r u s h zon e at the contact of the
quartzites and schists and its formation may possibly be conn e ct e d
w it h th e granit e intrusions of M ount He e m skirk rang e
A
p e trolog i cal examination of t he wall rock and or e would probably
show that the M ount L y e ll or e s lik e those of oth e r pyr iti c masses
e ls e where are m et asomatic repla c ements of the enclos i ng rock
The grea t faults which traverse the lodes are thought by some
writ e rs to hav e a genetic association with the ore bodies but thi s
co n nection has not y e t been proved The manner in which the
lodes are faulted and displa c ed horizontally by thrust faults
.
.
.
,
.
-
,
.
’
,
.
-
,
0
.
.
,
,
.
.
.
,
.
,
,
,
.
,
,
,
.
.
,
.
.
.
,
.
.
-
.
,
.
-
.
,
.
-
-
,
.
-
,
,
.
-
,
.
-
1
L
oc
.
cit.
,
p 1 18
.
2
.
L
oc
.
ci t.
,
1
1
4
p
.
.
44
MININ G G EOLOGY
.
contents wer e principally cerussite native silver chlorides
bromides and iodi de s of silver associated with kaolin garn e t and
quartz
Belo w the oxidised products c ame what are locally termed
sooty sulphides consisting of loose aggregates of galena and blend e
enclosed in a gangue of quartz and garn e t The friabl e sulphides
,
,
,
,
,
,
,
.
,
,
.
JA M I ES
ON
S
N fi c
rL
r
N 35
‘2"
S ca le
FI G
.
26 —
.
0
Fe et
Cro s ection o f Broke Hi ll L o de —B k n Hil l P
Mi e
( Copied f m t h Co m pa y p lan
s s
n
n
l e
.
io
n
e
’
3
e
p1 1e tary
1o
.
passed downward into solid sulphide s (blend e and galena ) enclose d
in a gangu e of quar t z garnet and rhodonite containing also i ro n
pyr i tes and a li t tle chalcopyrite The sooty sulphid e s w e r e
frequently very rich and apparently r e pres e nted a zone of
secondary enrichment
Bet ween the 2 0 0 and 300 feet levels th e lod e divides into two
spurs or branches which follow th e trend of the en c losing rocks
,
,
,
,
,
.
,
.
,
,
.
C LA S S IFI C A T I O N
OF
MIN ERAL D E P O S I T S
45
.
The wal ls of t he lodes are not slicken sided I n many places the
roc k is i mpregnated or r e pl ac ed more or l e ss wi t h or e
The gn eiss and schist ar e associated wi th numerous dyk e s of
1
dior i te to th e in t r u sion of wh i ch the fold i ng of t h e rocks and
subsequ e nt fillin g of the cavi ti es along t he axial l i n e of ma i n
fi e xu r e may be ascr i bed
The charac ter and g e n e s is of t his lod e is s t ill a ma t ter of d i s
2
agreement among Aus t ralian geologis ts P i t t man and Jaquet
conte nd t ha t th e lode is a large sa d dl e—reef e nclos e d in al t ered
3
se dimen taries P rof e ssor G r e gory on t he o th e r hand mainta i ns
t hat th e po si t ion of the lode has be e n determined by a s e ries of
powerful faults al ong which m i n e ralisa ti on h as tak e n place H e
con t en ds that the c onta ining rocks are no t sed im e n ta ry and n e v e r
w e r e Th e gn e iss e s and sch i sts beside th e lod e are h e a ffi r m s a
ser i es of altered igneous rocks Pi tt man and J aq u e t oppose t h i s
vi e w with t he statement t ha t the sa m e or similar gne i sses and
schis t s in t he adjacent dis t r i ct con ta i n bands of l i mestone which
cl e arly prov e a sed i menta ry origi n for the seri e s
B uc kton Or e D ep osi ts T e n ness ee — The pyri ti c ore bodies in t his
reg i on m ay b e tak e n as typical of t h i s class of ore depo s i t i n
Am e r ica Th e rocks consis t of gn e iss and micaceous sch i s t s or
sla t es wh ich have been thrown into close folds
-
.
.
,
.
.
.
,
,
.
.
,
,
.
,
,
,
.
-
,
.
-
.
.
FI G
27
.
.
— I deal S ec tion , N
.
W
.
to S
D uc kte n regio n
owing probab le tru ture o f
( A fter Henri c h )
.
E
sh
,
.
s
c
.
.
The ore bod i es consis t of masses of pyrrho t i te with wh i ch occur
sulph i des of copper zinc and le ad Th e port i ons near t h e surfac e
4
have been oxi dis ed into gossan Carl Henrich sta tes t hat b e low
G eo l ogy o f t h e B roken Hil l L ode a n d B arrier Ra n ges
J B
J aq u et
”
M in eral F iel d N e w S o uth Wale s M emoi r G eo] S u r vey N S W N o 5 1 8 94
2
T h e G enes is o f B roken 11111 L od e
E F Pittm an a n d J B Jaq u et
A u str a l ia n M in in g S ta nd a r d Oc tober 1 90 4
3 Pro fe
T h e G en es 1s o f B roken H ill L ode
s s or J
W G rego ry
A l elbou r n c A r gu s S epte m ber 1 90 4
C arl Henri ch D u c kto wn Ore D epo s its a n d T rea tment o f Copper Ores
T ra ns A m I ns t A L E v ol xx v 1 896 p 2 0 6
-
.
,
,
.
“
1
.
.
,
,
,
.
.
,
.
,
,
.
.
,
,
,
.
.
“
.
.
.
.
.
.
,
1
‘
,
,
.
.
.
,
.
.
,
,
.
.
46
MININ G GEOLOGY
.
the gossan and above the unaltered sulph i des there is a zone of
secondary enrich m ent consisting of partly oxidised c opp e r ore or
”
black copper
F requ e ntly a floor of whit e quartz o c curs b elow
the enrich e d zone frequently containing dispe rsed grains or
bunch e s of marcasite
The or e deposits do not occur in d i r e ct association with igneous
intrusions bu t are found along the planes of fa u lt fi s su r e s th e
fault plan e in all cases according to Henrich form i ng the east or
hanging wall of th e d e posit which is always sharply de fi n e d
That wr i t e r is of the Opin i on t ha t the B uckton ore depos i ts ar e
replac e ments of igneous dykes which at one tim e occupied th e
pr e s e nt places of the ore bodies
.
.
-
,
,
-
,
,
-
,
.
-
-
.
d
F
a h l ba nds
( )
.
Thes e are beds or strata of crystalline metamorphic rock so
highly i mpregnated with or e as to be of commercial value Th e
silver b e aring fahlbands (or gray beds ) of N e rway are among th e
best—known exampl e s They follow more or less clos e ly th e
strike and d i p of the gneissoid and schistose strata by which they
are bound e d They e xtend for several mil e s and in cases atta i n
a width of s e veral hundred feet
I n th e Kongsberg district t hese bands are crossed nearly a t
right angles by narro w fi s s u r e veins varying in width from a few
inches up t o 2 feet and are product i v e of silver only wher e
th e y in te rsect the fahlbands The fahlbands are important in th i s
distr i ct sol e ly from the fact that t he small fiss u r e veins ar e e n
riched i n passing t hrough them more esp e cially when two such
veins i nters e ct within the mineralised belt
,
.
-
,
.
,
.
,
.
,
,
.
-
,
.
FI G
.
28
.
—S ec tio n
of F
band at D k y S o nd N w Z
d
h
l
i
t
b
F
b
an
h
S
(
)
)
ah l
(
a
us
c
u
a
s s.
,
e
and
eal
.
( A fter
Park )
.
.
Sound in N ew Zealand there is a mineralised band
of mica and chlorite schists c ontain i ng pyrrhotite pyr ite with a
littl e chalcopyrite and nickel asso c iat e d with epidote and garne t
min e rals T h e band can be tra c ed southward across the moun
tains for several mile s but i t has not yet been shown to contain
a a b l e or e of any kin d
p y
Z
A t D usky
,
,
,
,
,
,
.
,
,
.
,
C LA S S IFI C A T I O N
MIN E RAL D EPO S I T S
or
47
.
Fahlbands are r e lated to bed impregnat i ons wh i ch probably
ow e t heir or i g i n t o a queous and gaseous emanations aris i ng from
-
,
a cooling intrus ive magma
.
( )
I t has sometimes happ e n e d t hat when a rock has been crack e d
or fis s u r e d a porti on of t he roc k on on e or bo t h walls has becom e
i mpregnated wi th some metallic su bs tance d i ss e mina t ed as grains
n e sts or bunches throughou t the mass in t h e vicini ty of th e
I mp reg n attons
e
.
,
,
,
fiss u r e
.
Such an occurrenc e is ca lled an imp regn a tion implying t ha t
th e m i n e ral has been introduc e d as a secondary produc t by
m i neral waters or superheated s tea m
The term impr e gnation i mpl ie s a ref e rence to th e genes i s
rath e r t han t he form of an ore—d e po sit and wh e n used i n a
morphologi ca l sens e i s somewha t va g ue and meaningless
G e net i cal ly the maj ority of s t ockwork s con tact d e posits and
fahlban ds may b e properly regarded as impreg na ti ons as well
as th e S i lv e r San ds ton e s of U ta h the Copp e r Conglom e rates of
Lak e Sup e r i or th e Copper Shales of M ansf e l d and th e G old
Bank e ts of th e Rand a ll of wh i ch probably d e r i ved th e ir me tallic
con te n t s from aqueou s and gas e ou s emanations e xpelled from a
cooling magma
—
The or e mo s t frequently found as an
T in I m p re g n a tio n s
i mpr e gnat i on i s cass it er ite or t i n s tone and t h e rock i n which it
occurs i n th i s mann e r is commonly gran i t e M any exampl e s of
t his class of t in d e pos it are me t w ith in Aust ral i a and i n
Tasman i a
,
.
,
.
-
,
,
,
,
,
,
,
.
.
-
,
.
.
FI G
.
2 9 — T in
G
n
ite
ra
)
(
a
.
.
( b)
I m pregn atio n
T in i m pregn atio n
.
.
M ount W i lls in Vi ctor i a ti n or e is foun d in veins and in
d i ss e m i nated grains i n a gran ite forming a true s t ockwork
A t Ve getable Cr ee k i n Ne w South Wal e s it i s found fi llin g
contraction cracks and j oints i n a granite near the j unction w it h
At
-
,
,
,
.
,
,
,
48
MI N IN G GEOLOGY
.
clay slat e s I n th e E mmaville division in the same S tate the
t i n b e aring ore occu rs in v e ins and i mpr e gnations in t he outer
crus t of a gran iti c boss
I n th e H e rberton di str i ct which produc e s the bulk of the tin
rais e d in Queensland th e t i n stone occurs i n veins bunch e s a n d
i mpregnat i ons i n gran i t e
1
A t t h e famous t i n m i n e at M ount Bischoff t h e ti n ston e occ u rs
i n str i ngs bunch e s v e ins and i mpregnations in quartz porphyry
e ur ite a n d topaz porphyry which have intrude d slates sandstones
and quar t zose rocks
I mpregnat i ons l i k e fahlbands form a group of metall i f e rous
d e pos i ts not very clearly de fin e d G enetically t hey are clos e ly
related to contac t deposi t s
,
.
,
-
.
,
-
,
,
,
.
-
-
,
,
-
,
,
,
,
-
,
,
,
,
.
,
,
,
.
-
.
(f )
S eg r eg a te d Ve in s
.
D e posits of this kind gen e rally occur i n the shap e of lenticular
masses , a n d oft e n succee d one another in l e ngth and d e pth in such
a manner as to const i tut e a more or l e ss conti n uous ve i n Th e y
are o n ly foun d i n s e d i m e ntary rocks that have b ee n sha rply folde d
wher e by cracks or fi s s u r e s have been form e d more or less parallel
w i th the bed di ng planes and d i pping at right angles to the axial
l i n e of e leva t ion
—
C h a ra c te ris tic s o f S e g re g a t e d V e in s
The ch ie f char
a c t e r is t ic s of s e gr e gat e d v e ins a r e as follows
Unc
e
rta
i
n
both
in
depth
and
lin
e
ar
e
xtens
i
on
1
that
is
they
5
( )
ar e s e ldom cont i nuous e i ther in l e ngth or d e p t h but occur
as a success i on of d i sconnect e d l e ntil shap e d mass e s
which may contain a f e w tons or many thousands of tons
of quartz
I
rr
e
gular
i
n
w
i
d
t
h
2
)
(
3
fi
S
e
ldom
possess
more
t
han
one
w
e
ll
wall
d
e
n
d
e
( )
4
F
requently
re
eiv
e
small
ve
i
ns
in
th
ei
r
course
c
( )
5
( ) Conform more or less to bedding planes of country rock
6
They
ar
e
only
foun
d
i
n
bed
d
e
d
s
e
d
i
mentaries
which
are
( )
gen e rally slat e s clayston e s or san dstones
O rig in o f S e g re g a te d Ve in s — Th e orig i n of segregated
d eposi t s of this class i s som e what obscure
Th e y g e n e rally occur
—
n
alo g the b e ddi ng plane of t he country rock Th e cav i t i es they
fi ll hav e appar e ntly b ee n forme d by th e fold i ng of the enclosing
rock 5 and th i s fol ding may hav e b ee n caus e d by secular earth
movem e nts or the intrus i on of an igneous mass
—
The pro ductiv e quar t z veins
N e w Z e a l a n d S e g re g a t io n s
1
H W F K ay ser
M ou n t
A n s t A s soc A dv t S ci en ce 1 892
.
,
,
.
.
,
,
-
,
,
,
,
.
.
-
.
.
-
.
,
,
.
.
.
-
.
.
,
-
.
.
.
.
,
.
.
.
,
.
C LA S S IFI C AT I O N
or
MIN ERAL D EPO S I T S
49
.
in th e Reefto n I nangah u a and L yell g oldfi e lds cons ist of a
suc c e ss i on of l e n t icular masses which generally conform to
the be dd i ng planes of the enclosing clays ton e s and sandston e s
Some of t h e larg e r or e bodies sw e ll ou t to a w i dth of 2 0 fe et a t
t h e ir w ides t part but the maj ori ty are shaped l ike fl a t lenses w it h
a thickness varyin g from 3 to 6 f e et Th e re are no dykes or
intru s ive boss e s i n t he v i cini ty of t he v e ins which oc cupy cav it i e s
formed along the bedd i ng planes of a monoc linal
S a ddl e R e e fs
These are se named from th e ir resemblance
in form to a stockman s saddle Th e y ar e mer e ly s e gregated v ei ns
formed in cavities along the bedding planes of sedimen ta ry rocks
wh i ch hav e been bent i n t o ant i clinal and syn clinal folds
1
E J D unn who worked out th e morphology of t h e saddl e
reefs of Bend i go g oldfi e ld in Vi c to ria de fin e s a saddle reef as z
“
A lenticular qua rtz lode lying between bed ding plane s of roc k
”
be nt over i n an ti clinal or syncl i nal folds
The chief chara c teristics of saddle reefs are as follows
,
,
.
-
,
.
,
.
‘
-
.
’
.
.
.
,
-
,
,
-
.
-
They occur in bedde d banded or folia te d rocks
They fi ll cavities which conform to the planes of bedding or
fol i a ti on of th e rocks
The gr e ate s t mass of ore occurs along t he crown of the
ant i cl i nal arch forming the s a dd le from whi c h the leg s
d e scen d on e on e ac h s i de of th e arch
The legs diminish rapidly in size as they des c end and
fi n ally die out
Two or mor e saddle—reefs may succ eed ea ch o ther in v e rtical
d e p t h under t he axis of the same anticl inal fold
Th e great e st thickness of ore in inv e r t ed saddle r e efs
form ed in synclinal folds is found along the axis of th e
trough
1
( )
2
( )
,
.
,
.
3
( )
,
4
( )
.
,
.
5
( )
.
6
( )
-
,
,
.
The saddle re e fs of Bend i go c onsis t of arch like mass es of gold
b ea ring qua rtz conforming to the bedd i ng plan e s of the enclos i ng
slate a n d sands ton e of S i lur i an age D unn has shown t ha t i n
most cas e s t he fol ding of the roc ks was caused by t he in t rusion of
i gneo us dyk e s
—
S
Th e gol d b e arin g veins at Cape
l
a dd e R e e fs
I nv e rte d
T e ra w h it i near W e llingto n l n N ew Z ealan d are interes t ing ex
amples of sad dl e r ee fs wh i ch e xh i b it bo th an anticlinal and
s yncl inal arrangem e n t as shown in fi g 3 1
Th e rocks ar e Triassic claysto n e s a n d sands tones which hav e
b ee n e rod e d i nto s tee p r i dges and de e p valleys wi t h th e resul t t h a t
th e veins have b ee n correspondingly denuded The or e bod ie s
M
ld
D
ept
o
f
ines V ictori a
e
E J D u nn R ep or t on B end igo G ol d
fi
M el bo urne 1 8 93
-
-
.
.
-
,
,
,
-
,
.
.
,
-
.
1
,
.
.
.
,
.
,
,
50
FI G
MININ G GEOLOGY
.
30
S
.
ectio
ns s h
.
o wi g Fo rmatio n o f S addle Ree f
n
-
s.
( A fter E J
.
.
D unn )
.
52
MININ G
G
EOLOGY
.
The ores m ost commonly found in gash veins are galena and
zinc blende V eins of t h i s class have no distinct walls and being
co n fi n e d to a singl e stratum of the formation in which they o c cur
are limited in exten t
-
,
.
,
,
.
FI G
33 — G
ealand
) S il rian l i me to ne
( b) S i l rian late
) G sh v ein o ntai ni ng galena nd b lende
(a
(c
.
.
ash V ei ns Wan ga peka
,
u
s
N
ew
Z
.
u
.
s c
a
,
s
a
s.
.
T
h
r u e F tssu r e Vein s
( )
.
V eins of this c lass are generally admitted to h a ve o rigin ated in
fi s s u r e s caused ei t h e r by se c ular folding or by ign eous int ru sio n s
,
,
and are believed to possess great depth They pass through all
kinds of ro c ks in their course independently of any bedding or
s tra tifi c a t ion 5 but in some part they may chan c e to c oincide
the dip and strike of the c ontaining formation
.
,
.
\
.
FI G 34
(a ) L i mes to ne
l
s
b
S
a
te
( )
.
.
L
~
e Fi
T ru
.
L L
—
L
_
re Vei n
( 0 ) G ra n ite
(d ) F i s su re vei n
ssu
.
.
-
.
.
The mineral contents of th e s e veins w ere d e pos i ted
asc e nding aqu e ous solutions wh i ch were probably gen e ti cally
connect e d with deep seated magmat i c intrusions
—
n
d
Th e ban ed arra gement of the v ei n matter of the fi ssu re vein s
of Cornwal l i s very si m i lar t o t ha t of t he solfataric v ei ns of th e
Hauraki g oldfie lds which would t e n d t o show th at t h e fill in g took
,
,
,
-
.
‘
-
-
‘
,
C LA S S IFI C A T I O N
or
MIN ERAL D EP O S I T S
53
.
place in t h e la t er stages of the aft er actions following t h e ign e ous
i ntrusion
T h e two walls do not always c oincide tha t is the fi ss u re is
ofte n a faul t and of va riabl e width A t ru e vein like a s e gr e gate d
vein m a y throw out spurs or branches from on e or bo th walls
L o de s O f Co r nw a l l — The lodes of Cornwall are famil i ar
e xampl e s of t r u e fi s sur e veins Th e y pass in d e p t h succ e ss iv e ly
through lim e ston e sla te and grani te I n t he limestone th e
princ i pal commercial produc t was l e ad 5 in the slate copp e r 5 a n d
i n th e granite t in
L o d e s O f B a v a ria n F o re s t — The thr ee gigantic qua rt z
1
lod e s on the slopes of t he Bavarian F ores t are r e garded by Suess
as the grea t es t monuments of lin e ar d i sloca t ion known in E urop e
Th e y are true fi ss u r e veins and are bel ie ved by tha t d i s ti nguish e d
geologist to oc cupy great faul t frac t ures on t he existenc e of which
he fi n ds suppor t for h i s cel e brated th e ory of moun ta in building
by h or sts a nd gr a ben
O f these the Asch lod e begins in the most north wes t erly par t
of Boh e mia no rth w e st of Asch runs to th e south eas t t rans
v e rs e l
a n d grani te of E rzg e birge
across
t
h
e
m
i
ca
schist
gneiss
y
M oun ta i ns 5 th e n cuts across t he narrow ou tcrop of gn ei ss n e ar
Se e berg d i sa ppears ben e ath t h e Tert i ary cov e r i ng in the bas i n
of F ranzensbad and E ger and r eapp e a rs immed i a tely on the o t h e r
sid e of t h i s in t he granit e m a ss of Sandan fi n a lly extending
through th i s up to th e sou t h of K onigs wart The to tal l e ngt h of
outcrop is nearly 2 5 mil e s
N ea r Hals where th e Asch l ode e nds th e re appea rs the begin
ning of th e gr e at v e in known as t h e Bohem i an Pfahl which strik e s
sou t h south e a s t th e n curves to t he eas t t h e n turns ba ck to th e
s t raight course and crosses the Bavarian front i er near F u r th
The l e ng t h of outcrop is abou t 3 4 m i les and t he av e rage wid th
about 10 0 fe e t F or a long d i s ta nce t h e lode runs bet w e e n t h e
gn e iss and hornbl e nd e rock but wh e re th e hornbl e nd e rocks ben d
it pass e s completely in to t he lat te r
Th e t hird and grea te s t of thes e lod e s i s the G r e at Pfahl It
s t rikes N 5 8 W and for th e gr e a te r pa rt of i t s cou rse vari e s
from 2 2 5 to 37 0 fee t w i d e F or a di s tanc e of 2 7 m i l e s in a sou th
eas t c ours e it separates th e granite from th e Triassic and middl e
Jurassic strata and then t o t h e w e s t of the chain passes com
l
l
into
the
Arch
ean
region
e
t
e
a
thenc
e
it
continues
in
a
s
t
raight
5
p
y
lin e as far as the Aust rian frontier Th e total length of outcrop
of this remarkable l ode i s 92 mil e s
Ve in s o f C rip p le C re e k — Th e gold bea ring v ei ns at Cripple
Cr e ek in Colora do traverse and e s i t i c t uffs and phonolite of low e r
1
Edu aid S u ess T he Face of the E a r th Engl i sh ed ition v ol i p 2 0 7
-
.
,
,
,
,
.
.
,
.
-
.
,
,
.
,
,
.
,
.
.
-
,
-
,
.
-
,
-
-
,
,
-
,
,
,
,
,
'
.
.
,
,
-
-
,
,
.
,
.
,
,
.
.
°
.
,
.
,
,
.
.
-
.
,
,
,
,
,
.
.
.
.
54
MININ G GEOLOGY
Tertia ry age They are
c e ntres of eruption
.
fis s u re
-
.
veins g roupe d around old volcanic
,
.
Th e cel e brat e d Comstock lod e in
N evada t rav e rs e s propyl i tised andesite dacite d i abas e diorit e
e tc of older Tertiary ag e I n the middle portion of i ts cours e i t
occupies the line of c ontac t between mass e s of diori te a n d
diabas e th e lat te r lying on th e hanging wall Th e bas e ment
1
rocks are grani t e schists slates and l imeston e s
The lod e has been traced for a distanc e of over
feet in a
nearly du e north and south dir e ction I t dips t owards th e east
and has a t hickness varying from 2 0 to 6 0 fe e t
Th e v e in
The vein —matter c onsists of crushed and
fi ss u r e is also a fa u lt
de c ompos e d rock clay and quartz The lode is r e markabl e for
th e high temp e rature of the mine water in the lower l e v e ls
Th e m in e s on the Comstock lode have yielded a fabulous
amount of gold and silver since they wer e opened in 1 85 9 The
gold exists as free gold associat e d with sulph i d e s of silv e r
—
M o th e r L o de O f C a l ifo rn ia
Th e G r e at M oth e r lode of
California is one of t he most remarkabl e fi s su r e veins in th e glob e
I t is trac e abl e for a distance of 7 0 m i l e s e xt e nding through fi v e
count i es and in many plac e s is a min e ralis e d belt ra ther t han a
tru e vein
Th i s immens e v e in or group of veins generally occurs in a b e lt
of black slate of Triass i c ag e and runs nearly parall e l with th e
plan e s of s tra t ific a tion dipping in th e sam e di rection at n e arly
t he same angl e of inclination A t d i ffer e nt par t s of its cours e it
traverses sla te diori te d i abas e s e rpent i n e a n d granit e
The mines on the M other lode and the rich placers on its
course hav e yi e ld e d a large propo rtion of t h e gold produc e d in
2
Cal i fornia for many years
L o de F o rm a t io ns o f K a l g o o rl ie —The famous lod e
format i ons of Kalgoorlie in Western Au s t ral i a poss e ss many
featur e s of pecul i ar inter e s t to the mining geologist
Th e y
are group e d t ogeth e r in an area about a square m i l e in e xten t
locally named th e G olde n M ile The country rocks i n t his area
have undergon e e xtreme alteration which ren ders the determina
t ion of th e ir original character very diffic u lt
I n th e oxidised ground there i s no sharp line of d e marcation
3
betw ee n the lode formations and the country rock which i s
C o m s to c k L
T he
o de —
,
.
,
,
.
,
,
,
.
,
-
,
.
,
,
.
,
.
,
.
.
,
,
.
-
.
.
,
.
.
-
.
,
,
,
.
,
,
,
,
.
,
,
,
,
,
.
.
.
.
,
-
.
,
.
,
-
-
,
e ke
eo og o
Co to k o e
W i gto
W
oe i t t
B c r,
G l y f th e
ms c
L d and
as h D s ri c ,
a sh n n , 1 8 8 2
M on ogr ap h tit of U S G eol S u rvey
2
h n y , T h e A n mf er on s C r a w ls of th e S ier r a N eva d a of
D
am r d , U S , 1880 , p 4 5
“
3
v r, T h e S u pe rficial l ra n f
s
rn u s ral an O re
H C
”
D s s , T ra n s A mer I ns t M in Eng , v ol xxv p 785
1
G
F
.
.
.
.
J
.
.
epo it
.
W it e
C b i ge
Hoo e
.
.
.
.
.
’
.
.
.
.
.
.
.
A te tio o We te
iii
.
.
.
.
A t i
.
A O
CL A S S IFI C T I N
or
MIN ERAL D EP O S IT S
.
ge n erally a dmitted to be of an e ru ptive chara c te r p robably of an
ac i d i c ho rn bl e nd e typ e
Th e lod e format i ons ar e beli e ved by s ome t o b e b e l ts of co u n t ry
rock more al te re d and m in e ral i s e d t han th e r e ma i ning rocks 5 by
othe rs to be ign e ous dyk e s wh i ch i n trud ed t h e old e r e ruptiv e s
and subs e qu e ntly becam e m i n e ral i s e d by asc e nding t h e rmal
wa ters i n t h e wan i ng or solfa taric phas e of e rup t iv e afte r actions
Th e schis tos e s t r uc t ur e obs e rve d i n t he lod e ma tter may hav e
been induced by t ang e n t ial st r e ss du e to s e cular foldin g a n d
e levation subsequ e nt to th e form ation of t h e lod e s Th e pr e senc e
of s e rici t e favours t h e V ie w tha t it was i nduced by pr e ss ur e
The e videnc e ava i lable a t pr e s e n t s ee ms to sugg e s t t ha t
m e tasoma t ic r e plac e men t on a larg e sca l e op e ra t ing along l i n e s
of fracture probably con t rac ti on fi ss u r e s played an i mpo rtan t
pa rt in t h e genesis of th e Kalgoorli e lod e s
The oxid i s e d po rt ion of t h e lodes exte nds from 5 0 t o 400 f e e t
below t he present surfac e the d e p th to which it e x te n ds b e ing
1
apparently i nd e p e nden t of e xis t ing wat e r l e v e l or surface con tours
Th e gol d in i t is fre e and extremely fine G enerally sp e ak i ng
the rich e r and more heav i ly min e ral i sed pa r ts a r e foun d to b e
2
oxid i sed to t he gr eates t d e pth
I n the oxid i se d zon e the lod e mat te r cons i s t s c h ie fl y of hydra te d
3
oxides of i ron hydrate d sil i cates of alumin a and magnesia
Calc i te
s e rici te chlorite and o ther alterat i on p roduc ts ar e also pres e n t
The lode formations ar e ofte n in te rs e c t e d by s mall v e in s of
4
decomposed qua rt z and Woodward states t hat i t is wher e t h e s e
are met wi t h that th e or e is rich e s t
Th e or e bodies or courses of rich ore oc cur in irregular l e ns
sha ped mass e s varying from a mere thread to many feet in wid th
They ar e no t con t inuous but occur in ech e lon — one l e ns over
lapping th e o t her
Below th e ox i d i sed zone t h e lod e s are mor e cl e arly de fi n e d
5
pa rt ic u larly i n the rich e r min e s
The c ountry rock is mass i v e bu t
e xtr e mely alt e red while t h e lode ma tte r i s sch i s to s e in places
show i ng al te ra ti on t o chlori te and s e ric i te and pl e n t ifully charged
wi t h d i ssem i nated iron pyrite
6
I n som e mines the vein fill in g consists c h ie fl y o f quart z
The
,
.
-
,
,
-
.
-
,
.
.
,
,
,
.
,
-
.
,
.
.
-
,
.
,
,
,
.
,
-
,
.
-
,
,
.
,
,
.
,
-
,
.
-
,
,
,
-
Hoo er l
Woodw”rd
T ell ri de D ep its
T
1
H C
H P
2
v
.
.
.
a
.
u
3
L
os
cit
oc
.
.
,
,
p 16
.
.
Pittman
o f We te rn A tral i
W Fre h eville
”
We tern A tralia
4
E F
.
.
,
s
us
5
s
6
L
,
us
oc
a
c
.
.
c it ,
.
.
p 1 44
.
p 7 58
“
T h e s e -cal l d L d
r a ns
I n s t M in a nd M e t
oo. c it
,
.
.
,
s on
e
o e
.
.
.
ote
”
N
.
.
,
th e
Geol ogy
an
F ormatio ns
,
v ol . Vi
d M
o f Hannan
p 17
.
.
s
a
s 0
1
ote
i it to
.
.
.
o
.
.
.
v
i e
.
.
an d
Portio
v ol vi p 1
o
TV
S
r
l
u
r
v
e
M
d
s
o
G
eo
S
R
e
co
f
,
f
y
“
al
t h e G ld M n s a
N
s on a V s
i , 1 8 98 , p 1 4 1
T ra ns I ns t M i n a nd M et , v ol
.
s
.
i er l D epo it
n
’
.
.
ns
.
t K goorlie
.
.
,
56
MININ G GEOLOGY
.
quartz however is in many cases replaced by calcite which is an
important gangue material sometimes occurring in larg e mass es
1
with calav e rite
The gold o c curs mainly in tellurides and sulphides only a minor
proport i on e xisti ng in t he free state
The prin c ipal accessory
min e rals ar e magneti t e siderite iron pyrites and ars e nical
pyrites
The tellurides occur as veins splashes and disseminat e d minute
crystals throughou t th e entir e m ass
M o u n t M o rg a n L o de — The great ore body in M ount M organ
mine in Queensland is b e li e ved by some to b e a huge pyriti c lode
I n the upper part of the deposit it c onsists of siliceous h aemat i t e
or g os s a n often with a porous c avernous structure ; and in th e
lower part of massiv e pyritic gold b e aring or e A zone of
,
,
,
,
,
.
,
.
,
,
,
.
,
,
.
-
.
.
,
,
,
-
,
FI
G
.
35 —
.
.
C ro
e tio n o f M o nt M organ L o de ( A fter E J D nn )
d b) S a d to ne
t
( ) Cell lar i li ceo
D yke
( f ) S i li eou ul ph i de
I gneou ro ck
( 9) O x i di e d e ri h e d zon e
s s -s c
(a an
(c)
(d)
u
n
s, e c
s
.
.
u
e
s.
s
us o re
s s
c
s
.
.
s.
n
s
.
u
.
c
.
secondary enrichment of g re a t value was met with in the oxidised
zon e
2
—
The a c tion of s e a water is held by E J D unn to s u ffi c ie n tly
account for the secondary oxidised or e s without calling in th e a i d
of thermal spri n gs as contended by D r J ack
The country rocks are highly metamo rphosed strata of P e rm o
1
N ote s on th e Co u n try R o c k s o f th e K algoorl ie G ol dfield
G W Card
Western A u stralia Res
of
th e C ool
S u r v ey of N S IV
v ol
vi
Part I
2
E J D u nn
M o u nt M organ G ol d M i n e
P r oc R oy a l S ociety of
.
.
,
,
.
-
“
.
.
,
,
,
.
.
.
“
.
,
.
Vzctor ta , 1 90 5
'
.
,
.
.
.
,
.
.
CLA S S IFI C A T I O N
MIN ERAL D E P O S I T S
OF
57
.
Carboniferous age trave rsed by in t rusions of hornblende g ranite
1
a n d dol e r ite
Th e or e body i t s e lf i s nearly su rrounded by dykes of dol e rit e
oft en al te red and s e rp e nt i nised
Th e e vidence suppli e d by D r J ac k W i lk i nson and o t h e rs se e m s
to ind i cat e t ha t t h i s un i qu e lod e 18 a t ru e fi ss u r e v e in g e n eti cally
conn e c te d w it h t he in t rus i on of t he dol e ri te s It bears many
po i n t s of r e s e mblanc e to t h e famous copp e r contac t d e pos i ts a t
Rio T i n to m Spa i n
Th e d i s ti nct i on b et w ee n contac t—
d e pos it s and fi ss u r e veins i s one
of geologic occurr e nc e ra t h e r t han genetic origin As will b e
shown la t er t he afte r ac ti ons of a magma t ic int rusion may b e th e
g e ne ti c cause i n th e forma ti on of fi s su r e veins con tac t—
d e pos it s
or e v e n b e d i mpregnation
—
Th e t in lod e s of t h e M alay
T in L o d e s O f M a l a ys ia
Penins ul a t h e e rosion of wh i ch has produc e d th e valuabl e alluvial
plac e rs of the S t ra i ts S ettl e m e n ts ar e fi ss u r e v e ins pass i ng from
2
clay sla te s downward i n to t he bas e m e n t rock gran it e
I n t his ri ch g o ldfi e ld a
G o l d Ve in s o f C h a rte rs T o w e rs
large nu mber of t h e v ei ns ar e enclosed in gran it e but som e occur
in porphyry Th e v e in gangu e is pr i nc i pally quart z con ta i ning
i ron pyr ite s and oft en pyrr ho t ite bo th of wh i ch con ta i n gold
C o p p e r L o de s o f B u tte C ity
Th e copp e r—
d e posi ts n ea r
But t e C ity i n the S tate of M ontana are among t h e rich e st 1n t he
glob e T h e co u n t ry rock l s grani t e t rav e rsed by dykes of rhyoli te
3
t r e nding nort h and sou t h
A numb e r of minin g companies are opera t ing on a lod e or
min e ralised belt w hich can b e t raced for ov e r 3 miles i n a
c o u rs e r u nn i ng nearly e ast and w e s t
Th e dir e c t ion of t h e min e ral b e l t follows the g e n e ral trend of
t h e fi ss u re plan e s which ar e approxi ma t ely pa rallel to e ac h oth e r
i m itin
in
plac
e
s
runn
i
ng
ou
t
uni
ti
ng
again
a
n
d
g
E mmons conclude s that t h e grani te was fi s s u r e d by t h e rhyoli te
i nt r us i ons wh i ch w e r e followed by t h e usual sequ e nc e of erup t iv e
—
after a c ti ons includi ng a t one s t ag e t he c i rc ul a ti on of hot asc e nd
ing solu t ions Through th e ag e ncy of t h e se solutions t h e g ran ite
be ca m e decompos e d along t h e l i n e s of fractur e and t h e ore—bodies
form e d by metas omatic i nt e rchang e
M uch of t he ore occurs i n t h i n interlacing v e i n s s om e of it
impregnating th e grani t e a n d some as hug e or e m a sses
1
C S Wilkins o n N otes o n a C o llec tio n o f R oc k s a n d M i n eral s fro m
”
M o u nt M organ Rea irds of G eol S u r vey of N S W1 1 891 v ol ii 86
2
W H D e 1 r ick N ote s o n Lo de T i n M inin g iii th e M alay e n in sul a
T ra ns I ns t M i n a nd M et v ol v ii 1 898 1 899 p 1 2
E mm on s
T h e Copper Res o urc es o f t h e U nited S tate s
T r a ns
-
,
.
-
,
.
,
,
.
-
.
-
.
-
,
-
,
,
-
.
.
,
-
,
.
-
.
,
-
.
,
,
.
-
.
,
,
-
.
,
.
,
,
.
,
,
,
.
,
,
,
.
,
.
,
-
,
.
.
.
,
.
.
,
.
,
,
.
.
.
.
'
.
.
.
,
.
,
.
.
.
“
,
,
,
A me r I
.
ns t.
M in E ng ”
.
.
.
,
v ol . x i x .
p 6 78
.
.
.
58
MININ G GEOLOGY
.
The oxidised portion carried silve r mainly the chloride a nd no
copp e r of any moment down to a depth of about 400 fe e t wh e r e
a zone of secondary e nrichment was met with c on ta in l n g r i ch
oxysulphides and other secondary ores of copper B e low this zo n e
app e ared the n ormal sulphide ore which consists principally of
chalcopyrite bornite and copper glance con taining
1
10 per cent of c opper and a li t tle silver
The width of the lod e s varies considerably but on a n average
may b e t aken at about 10 f ee t
,
,
,
,
.
,
.
,
,
,
,
,
.
.
,
.
1
I
D o ugla s
nst
.
,
M i n En g
.
T he
.
,
Copper Re o r e o f
l xi x p 6 79
vo
s u c s
.
.
.
.
th e
U
nited
S
t te
a
s,
T r a ns
.
A m
.
60
MININ G GEOLOGY
( b) A decrease of pressure
.
.
E lectro chemical act i on
Ch e mical pre c ip ita t ion
B y oth e r contact with oth e r min e ralised solutions
B y gas e ous emanations
( )
d
( )
8
( )
(f
(9)
0
-
.
.
.
.
By
absorption of metals by gelatinous sili c a etc
,
.
The solutions eith e r found th e
caviti e s awaiti ng them or they formed t h e ir own channels by a
process of slow progr e ssiv e replac e ment of th e wall rock parallel to
pr i mary fractures
I f the cavit ie s wer e pre existing they wer e formed mechanically
by forc es either ( 1) in ter na l or ( b) e txer na l to the rock a fi e c te d
I n the case of e ruptive magmas unequal cooling of the igneous
mass would tend to cr e ate unequal internal tens i ons with the
r e sult that fi s su r e s of contra c tion would be formed M agmas like
t h e mol t en charge in a blast furnace will cor r ode the walls of
“
t h e ir cavern and th e plucking ac t ion of the rising pasty mass
1
will tend to detach fragments from the roof and sides D aly
conclud e s tha t the diges t ion of solid ro c k by a magma causes an
i ncrease of volume of the magmas ther e by furnishing su ffi c ie n t
e nergy to fracture t he overlying rocks and force the magma itself
along planes of weakness
Sedimentary and older erup t ive rocks may be fractured by an
igneous intrusion or by the lat e ral and tangential s t r e sses created
by the secular folding of t he cr u st of the earth Such forces ar e
ext e rnal to th e rock mass affected 5 and if w e consider the manner
i n which they act we shall fi n d that igneous intrusions play a
more important part in the genesis of vein cavities than the more
pond e rous s e cular earth movements
Secular movement i s extrem e ly slow s e ldom ex c eeding a f e w
inches in a c e ntury T h e folding wh i ch i t causes being for th e
most part of wide stru c tural or t e ctonic importance is contin e ntal
rather than local
When the stress exce e ds the e lastic limit
of th e mat e rial the resultant e ffects are faulting and shearing
plication and sharp infolding
Th e fractur i ng which produces open fi ss u r e s and caviti e s is
c h ie fl y the work of igneous intru sions a n d volcanic forc e s
Th e s e
agencies having mad e the cavities also provide the mineralised
gases and solut ions that corrode and r e place the shattered r ock
and fill the fi ss u r e s with mineral matter
O r e bodies a re often formed along j oint and faul t planes and
at the interse c tion of j oints simple fractures and faults A
O rig in
of
Ve in
C a v itie s
—
.
,
-
.
-
,
'
4
.
,
,
.
,
,
,
.
,
.
,
.
-
,
-
-
.
,
.
,
.
,
.
.
,
.
-
,
,
,
1
Dal y R A
xvi p 1 0 7
.
,
v ol .
.
.
.
,
,
M
1 90 4
e ha i
c
.
n cs
o f I g eo
n
us
Intrusio n
,
A mer
.
.
J ou r n
.
S et
.
O R E y a ms
61
.
typical example of this class of depos it in Bend i go
1
V ictoria has been shown by T A Rickard
,
FI
G
.
36
ody at Inter ec tion o f Fract r
A R i kard )
S an d to n e
( b) S late
(cc ) Fr cture
Go ld b ari g q rtz i th form o f a f l
dd l
d
Ty
-
.
pi
ca l
S
e tion o f O
( A fter T
c
re
.
(a )
(d )
.
.
.
l
fi
l
o
d
e
d
,
g
s
-
B
c
.
.
ua
n
.
.
a
.
n
e
u es
s
s
a se -sa
e
e re
.
.
The sulphid e ores of M onte Cristo in the S ta te of Washing ton
2
ar e stated by Spurr to be replacem e nts of t he coun t ry rock
The ores which are c h ie fl y gal e na blende chalcopyr i te
t onalite
pyri t e and a rsen o—pyrit e are concentra ted along j oin t plan e s and
i nt e rsections in t h e mann e r shown i n the nex t fig u re
—
I t som e times happens t hat the lod e s
A g e O f Ve in F il lin g
in a dist ric t a r e of different ages and that t he m e mbe rs of on e
Vh e n
syste m make an an gle with t h os e of anoth e r system W
d i splacement ta k e s place i t i s e vid e n t that t h e vein which
d i splac e s another vein is younger t han the displaced v e in
I n the case of large fi ss u r e s now fi lle d wi t h min e ral mat t er i t
is highly imp robabl e tha t they remained as op e n chas m s w i thou t
suppor t unt il th e y were filled It is g e nerally beli e ved that i n
th e beginning t h e fiss ur e s w e re of small s i z e and gradually
,
,
-
,
.
,
,
,
,
,
.
.
,
.
,
.
,
.
,
ik
p
T A R c ard T r a ns A m I n st M E , v ol
2
s
s
fM n
rs
J E S u rr
O re D
'
R ep or t U n ited S ta te s G eol S u rv ey , 1 90 0—1 90 1 ,
1
.
.
.
.
,
.
epo it o
.
.
.
xx
p 469
as h n n ,
,
art I I p 8 49
.
o te C i to W
P
.
.
i gto
.
.
.
2 2 nd A
n nu a l
62
MININ G GEOLOGY
.
in c re a sed in length depth and width as th e min e ral matter
a cc umulated in them to a fford the necessary support I n other
words the e n largement of the lode was the work of m e ta somatic
replacement operating upon the rock forming the walls of the
orig i nal fi s su r e
I t might be expected that it later movement took place it
would t end to follow an old line of fi ss u r e rather than initiate a
new one and in support of th i s view there is internal ev i dence i n
many lodes that they have been reopened at different periods
Port i ons of the M artha lode at Waihi have been brecciated by
,
,
.
,
.
,
,
.
S C A L E O F FE E T
5
FI G
.
3 7 — S ketch
e tio o f T nnel d Vei Expo re in V ertical C liff
h o wi g m i nerali tio n al o g j oi t
G la ier C re k
probab ly
by
S h ade d are
repre ent i m pregn tio o f to alite
de en di g w ter
ometi me be o ming o li d ore
A
f
te
r
w it h
l p h i de al o n g j oi nt
(
S p rr
e
c
n
sc
s
an
u
n
s
,
a
n
su
as
s,
,
n
sa
.
s
su
u
n
s c
-
.
n s
s
s
s
a
c
s
,
,
n
n
s.
.
wall movements and r e cemented 5 and evidences of a similar
character are not uncommon elsewhere
1
Weed who mad e a special examination of th e copper v e ins of
Butte in M ontana states that the veins there are of s e veral ag e s
and syst e ms and that the older primary quartz pyrite veins were
reop e ned by later movem e nts which he corr e lates with a period
of volcanic activity This reopen i ng he says result e d in the
d e pos i tion of the copper sulpharsen i de e n argi t e which i s n o w
found to b e the chief ore of some of the veins
As a rule the formation of vein matter took place after the
formation of t he enclos i ng rock
1
W H Weed O re D epo s itio n a n d Vei n E nri c h m en t by A scending Hot
Waters T r a ns A m I nst M E v ol xxxiii 190 3
-
-
.
-
,
,
,
-
,
,
,
.
,
,
,
.
-
.
“
.
.
,
,
.
.
.
,
.
.
,
.
0 111: VE
IN S
63
.
I n many lod e s ther e is evidence that t here w e re sev e ral p e riods
of ore formation Recent inves t igat i on has shown tha t t he ag e
of a l ode may be of compara ti vely late date even in v e ry old
-
.
,
rocks
The m e talliferous andesitic rocks in South Amer i ca Ne va da
T ransylvania and Ne w Z e aland were erup t ed i n middle Tert i ary
times ; hence t he con tained ve i ns must b e of later da t e probably
of ol der Pl i oc ene age The major i ty of v ei ns occurring i n clastic
roc ks ar e supposed to have be e n formed in later geological t ime s
W idth O f L o de s — L odes vary considerably i n wid t h bo th
along their cou rse and in depth Th e Comstoc k lode i s i n par t s
2 00 fe e t to 30 0 feet wide and in oth e rs no t more t han 2 0 fee t
The Premier lode at T e A roha va r ies from 2 0 feet to 60 feet wide
and s tands up like th e wall of a hous e along t he flanks of the
mountain for m i l e s The M artha lode a t Wa i hi var i es from 10
.
,
,
,
,
.
.
.
.
.
,
,
,
.
FI G 38 — S h o wingLE ffec ts o f Faulting
Be fore faulting
( b) A fter f ulting
.
(a )
to
,
.
.
a
.
.
feet wide The Bohemian Pfahl in a leng t h of 34 m i l e s
main tains an average width of 1 0 0 f e et but in places widens out
to 3 7 5 f e et wh il e t h e G reat Pfahl in its c ourse of 92 miles varies
from 2 2 5 to 3 7 0 feet in width
The varia t ions i n w i dth may b e du e to sev e ral caus e s Th e
rock may hav e yi e lded more a t on e po i n t than a t another dur i ng
the formation of th e fi ss u r e
A fractur e t hat pass e s t hrough al t erna ti ng bands of hard and
soft rock generally follows a sinuous cou rs e ; for wh i l e th e
frac tur e t e nds to pass t hrough the soft er rock in a d i r e c t ion
normal to its course the res i stance offered by t he har d rock
caus e s i t to tak e the sho r test d i stance t hrough the resis ti ng
med i um wh i ch w ill be a cou rs e a t r i ght angles to the bed ding or
90
.
,
,
.
.
.
,
.
,
When faul ti ng tak e s place on t he walls of such a sinuous
fiss u r e th e result is a succ e ss i on of w i de and narrow cav itie s as
shown i n fi g 38
,
,
.
.
64
MININ G GEOLOGY
.
The Temperance lode in th e Ne rr e na or L ittl e Bend i go g oldfi e ld
in Vi ctoria is a typical e xample of an ore body compos e d of a
1
string of loz e nge shaped mass e s Accord i n g to W Bradford the
lod e traverses a seri e s of alterna t ing sla t es and sandston e s of
Silurian ag e I n vertical d i stance it cons i sts of a succ e ssion of
w ide and narrow parts the wide pa rts forming in th e slates and
th e narrow in the harde r sa n dstones as drawn i n the accompany
ing fig u re which however does not show any appearanc e of
faulting
Again i t is poss i bl e that erosion either chem i cal or mechanical
hav e act e d in one portion of a fis s u r e mor e than in another
-
-
,
.
.
,
.
,
,
,
,
,
.
,
,
,
.
FI G
—
S e c tio n
39
.
.
ates
sl
o f T em pera e L o de h o wi g m k
f q rtz in
S le 1 i
to 40 ft ( A fter W Bradford )
nc
ca
.
n
,
,
.
s
n
.
a
es
o
ua
.
.
L odes are generally widest in soft or moderately soft ground
and narrowes t in hard rocks such as unalt e red granit e and e site
and d i orit e I n hard rock a lode will frequ e ntly d windle down to
a m e r e crack or clay parting and expand to i t s normal siz e on
enter i ng softer c ountry
L e ng t h o f L o d e s
The longest lod e s ar e g e nerally th ose
which are broadest O f the thr e e gr e at lod e s trav e rsing th e slopes
of the Bavarian F or e st the Asch lod e is traceabl e for a dis tance
of 2 5 mil e s th e Bohem i an Pfahl for 34 mil e s and th e G rea t
Pfahl for a leng th of 92 miles
I n Cornwall the average length of a loa d is about a m i l e in
Saxony 3 to 4 mil e s and i n t he Harz M ounta i ns 8 t o 10
,
,
,
,
.
,
.
-
.
.
,
,
.
,
,
1
W
B
.
ra dford
1 90 5 , p 6
.
.
,
B
u l l etin
N
o
.
15 ,
C eol
.
S u r ve y
f
o
e bo r e
Victor ia , M l
u n
,
O RE V E
m il e s
IN S
65
.
I n California the G reat M other lod e has be en t raced for
ov e r 7 0 m i l e s
I n t h e Hauraki g oldfi e lds in N ew Z e aland t he T oka te a lod e can
b e trace d for 3 m i l e s 5 the Wa i ota hi lode 2 mil e s 5 t he Pr e m ie r
lode T e Aroha 4 miles
I n many mini ng d i str i c t s t h e
S trik e o r B e a rin g O f L o de s
main lod e s possess a gen e ral bearin g Thus in C ornwall t h e
g e n e ral s t rik e i s E N E
and i n th e no rth of E nglan d E
I n Prussia many of th e iron lodes s t r i k e N a n d S I n
and W
t h e Hauraki g oldfi e lds th e trend of th e mos t produc t ive lod e s i s
NN E
O n the o t h e r hand t he lod e s i n t he F re i b e rg
dis tric t run i n var i ous direc t ions
A chang e of s t rike has som e
t i m e s an in fl u e n c e in the enrichm ent of a lod e
I n som e mining regions th e r e is a gr e at sim i lari ty in the con te n t s
of th e lod e s runn i ng i n the sam e dire c ti on Thus in Cor nwall t h e
E N E lodes yie l d ti n copper and a l it tle l e ad while t h e N S lod e s
yi e l d clay and l e ad Bu t the e xcep t ions are too many to allow a
sa fe g e n e ralisa t ion to be made
—
o
L
The d i p of a lode may vary as i t
I n c lin a ti n o f
0 de s
d e scends i n depth or may vary a t diffe re nt points along i ts cours e
The dip is spoken of as fla t or st e ep I t is always at right angles
to the str i ke
The Samson lode at Andr e asb e rg the Tal i sman lod e at
Karangahak e and th e E mpire lod e i n t he Wa i hi m i n e i n N ew
Z e aland dip in opposite direct i ons i n d i ffe r e nt par ts of th ei r
cours e
M oiss e n e t i n h i s classi cal work on th e L od es of Corn wa ll
fully endo rses t h e g e neral i sat i ons of Henwood r e la ti ng t o t h e
in fl u e nc e of inclination str i ke and charac te r of cou nt ry upon t h e
cont e n t s of th e lod es of that country With r e spec t to th e se h e
formulat e d the following laws
Th
1
e se parts of t h e lod e w hos e i nclina ti on is most n e a r l v
( )
v e rtical ar e always t h e most productiv e
I
n
th
e
r
i
ch
par
t
s
t
h
e
lo
e
is
enclos
e
d
in
coun
t
ry
of
mode
d
2
( )
ra te hardn e ss
? or
i
d
The
courses
shoots
g
e
n
e
rally
i
n
t
h
e
same
3
p
( )
dir e ction as the country and very oft e n also th e gro u ps
of bunches con t ained i n th e sa me lode
Th
e
bearing
of
the
rich
par
t
s
i
s
g
e
n
e
rally
t
hat
of
t
he
4
( )
stratigraphica l sys te m w it h wh i ch t h e in iti al fracture of
the lod e i n t h e r e g i on und e r obs e rva ti on is conn e ct e d
Thes e laws hold good for th e lod e s of Cornwall It is doubtful
i f t h e y can b e saf e ly applied in o ther min i ng r e gions and e ach of
th e m has b e en d i sprov e d in d i ffe rent pl a c e s
Take th e fi rs t law The richest bonanzas in the Tham e s gold
.
.
,
,
,
,
.
,
-
.
.
.
.
.
.
.
.
.
.
,
.
.
.
.
.
,
,
.
,
.
.
.
.
.
,
.
.
.
,
,
,
.
,
,
,
,
.
.
.
“
“
,
.
.
.
,
.
.
0
66
MININ G GEOLOGY
.
were found in t he Caledonia and Cambria reefs in places
where the angle of dip was und e r
Both above and below t he
bonanzas th e d i p was abou t
D e p th O f L o de s —With the exception of gash v ei ns which
ar e wedg e shaped openings from t he surface t he d e pth whic h
ve i ns may attain has not yet foun d a l i mit
Th e greatest dep t h to w hich a lod e has be e n followed down
wards i s at P rz ib ra m in Boh e m i a wher e on e of the min e s has
reached a depth of n e arly 4 00 0 f e et and is still being de e p e ned
Th e gold min e s of V ictor i a and the copper mines a t L ake Superior
have reach e d depths ranging from 2 00 0 feet to 5 0 00 feet
It s e ems l i kely that fi s s u r e v e ins will des c end to a greater dep t h
than min i ng operations can follow them
The gangue or matrix of
A rra ng e m e n t o f L o de M a tt e r
mos t veins is quartz Th e most notable exception is lead which
ofte n occurs i n v e ins of calcit e or fl u or spar
The quartz may b e fl in ty or chalce donic fin e ly or coars e ly
crystallin e I t may b e ba nded r ibbon like co n centric brecciat e d
fi e ld
“
,
-
,
.
-
.
,
,
,
.
-
-
.
-
.
-
.
.
,
-
.
,
-
.
FI G
,
,
.
40
.
—S h o wi ng
R
,
ibbon S tru t re o f V i
c u
e n
Matter
.
compact vuggy granular d i sseminated or in loose sugary grains
The arrang e m e nt of the lod e ma tt er should always be obs e rved
s i n c e the structure and arrang e men t will almost al ways tell u s
someth i ng about it s history
I n lodes of the base m etals the contents are somet i mes arranged
in bands or layers parallel to the walls the minerals a nd ore s
,
,
,
,
.
-
,
.
,
68
MIN IN G GEOLOGY
.
I n Cornwall and elsewhere experi e n c e has shown that the occur
rence of a horse is often attended wi t h an enrichm e nt of the
con t ents of the lode a c i rcumstance whi c h doubtless originate d
the Corn i sh aphorism A h or e p a ys f or itself m e aning that
the incr e ased richness of the l od e more than comp e nsa te s the
extra labour and expense of working caused by th e app e arance of
th e hors e
I n the steeply incl i n e d gold bearing v e ins of the Thames horses
of rock were oft e n m e t with and in a lmost every i nstan c e they
caused local enrichm e nt the increased val u es being generally
c o n fin e d to one split or branch of the lod e
I nvest i gation showed t hat this enr i chm e nt was not due t o a
concentration of the valu e s into on e branch but to an ac t ual
increase i n the mean valu e s previously rul i ng in the main lod e
1
—
O u tc r o p s O f Ve in s
Professor Van His e dist i nguish e s th e
diffe rent zon e s of ro c k alteration by a nomenclature suggested by
th e biologi c al terms used to d e s i gnat e the som e what parallel
changes i n animal life His subdivisio n s ar e as follows
,
s
,
,
.
-
,
,
.
,
.
.
-
.
1
.
Z
a
.
b
.
2
.
.
.
f
Z
Ka ta morp hism
f
B e lt of weathering
Bel t of cementat i on
on e o
on e o
A
n a mmp
h zs m
.
’
.
Th e Katamorphi c zone is that in which co mplex c ompounds ar e
brok e n down and altered into S i mple compounds I n othe r words
it is th e zon e of oxidation
I n t h e Anamorphic zon e th e alt e rat i on of rock masses results in
th e production or build i ng up of compl e x compounds from simpl e
compounds
The belt of weath e ring extends down from the surface to
—
groun d water level th e belt of c ementation from ground water
lev e l to th e zone of Anamorphism
Ch e m i cal action is very active in the zone of Katamorph i sm
and is in most cases accomplished by descending solutions Th e
changes effected in this zone are : ( a ) oxida tion (b ) h y dr a tion
and (c ) c a r bona tion
B y long c ontinued e xposure to atmospheric ag e nci e s and t he
action of desc e nding met e oric waters th e o u tcrops of iron copp e r
and silver sulphide lod e s are often oxidised and so altered by
removal a n d replacem e nt as to bear lit tl e res e mblance t o the
unaltered vein matter which will generally be found at a greater
depth
“
C h as R i ch ard Va n Hi se A T reati se on M etam orph i sm U S C eol
Wash i ngton 1904
S ur vey
.
.
.
,
.
,
.
,
,
.
-
,
,
,
-
.
1
‘
.
.
,
,
.
,
.
.
.
O R E VE
IN S
69
.
The iron sulph i d e s ar e ox i di s ed fi rs t to sul pha tes a n d t h e n t o
ox i de s while t h e copper is r e move d by wa te r i n t h e form of
solubl e s ul phates or i s o xid i s e d to carb ona tes wh i ch s ta i n th e
rocks gre e n and blu e S i lv e r sulph i des a r e al tere d to th e chlor i d e
n ea r t h e surfac e or the d i s solved m e tall i c con te n ts are found
conc e ntrated at or b e low wat e r l e v e l
I n many sulp h ide lod e s i ron is th e predomina t ing cons t i t u e n t
and i t s oxida ti on g e n e rally r e sults in t h e ou t crop assu ming a
porous hon e y combed appearance t h e removal of t he sul ph i de s
leaving cavit ie s which ar e only pa rt i ally fi lle d wi t h ox i d e T h e
ferruginous solution fl o win g from the ou tc rop s ta ins and d iscolours
th e s u rrounding rocks and so i l
Such ironstone outcrops ar e kn own as g ossa n in Cornwall tr o n
h a t i n G ermany and ir on s t n e blows in Aus tralia
Th e na t ure of th e gossa n va ri e s wi t h the cha ra cter of th e
orig in al sulph i d e or e body I f much qua rt z is pr e s e n t the ou t
c rop is cav e rn ous and cind e ry red or brown colour ed 5 but if th e
or e —body is compos e d mainly of iron pyri te s t h e gossan w i ll cons i s t
of ochr e a n d bro w n h aema tite of te n in bo t ryoidal and s ta l ac titi c
forms
The oxidation and l e ach i ng of lod e mat te r has often proc ee d e d
to a dep th of 5 00 f ee t be low the surfac e outcrop i n some cas e s
far b e low th e pr e s e n t wa te r l e vel Som et ime s t her e is a sharp
line of de marcation betwe e n the o x idised and unaltered po rt ion s
of a lod e but mor e ofte n t h e passa g e i s gra dual the s u ph ide s a t
fi rs t making t h e ir appearanc e in d eta ched nodul e s bunch e s or
small lenticular masses which gradually beco me mor e pl e n t iful
wi t h increasing d e p th
A gos sa n is always an indi c ation of a lod e b e lo w a n d for t hi s
r eason forms a valuabl e guid e to t he pros pec tor
G ossan outc rops shoul d be ca r e ful ly sa mpl e d and assay e d as
th e y may contain valuabl e min e rals t h e pres e nce of which co ul d
not be d e te cted by pan n ing
Th e valuabl e gold a n d s i lv e r lodes of th e Ha u raki g oldfie lds
give little or no indica ti on of the i r valu e by crush i ng and panning
The gold exists in such a fi n e ly div i d e d s ta te tha t a c olo ur is rar e ly
s ee n i n t h e or e and t h e valu e can only b e asc e r ta i ned by car e ful
sampl i ng and fi r e as say
Th e r i ch unox i dis e d sulpho tellurid e or e s of W e s te rn Aus t ral i a
possess no phys i cal fe atur e of a s t r i king charac t er to in di ca te
t h e ir gr e at valu e and wh e n tested by t he pros p e ctor s ready
method of rough crushing and panning app e ar valu e l e ss
E ach min e ral poss e ss e s cer ta in charac te rist i c indica t ions pecul iar
to its e lf and must be co n sid e red separat e ly Thus an i ri de sc e n t
film or layer of oil on a poo l of water or an emanation of car
,
,
,
.
,
-
.
,
-
,
,
.
.
,
o
,
.
-
.
,
-
,
,
,
.
-
,
-
.
,
,
,
,
,
.
,
,
,
.
,
.
.
,
-
.
-
,
’
,
.
,
.
,
70
MININ G G EOLOG Y
.
hydrog e n may dir e c t att e nt i on to the existence of
petrol e um in the vicin i ty
Brine springs point t o d e posits of salt and chalybea te S pr i ngs
to iron though not n e c e ssarily of commercial value P u ffs of
steam or the smell of sulphur e tt e d hydrogen in a volcanic r e gion
may point to th e exist e nce of sulphur F or instanc e at Rotorua
and White I sland in Ne w Z e aland extensive deposits of sulphur
ar e found around the num e rous fuma roles both activ e and
extinct and at both places the odour of sulphuretted hydrog e n is
plainly p e rc e ptible long b e fore t he deposits ar e reached
—
Co n dit io n o f M e ta l lic Co n t e nts o f V e in s
G old occurs
in t h e native or uncombined form but at Cripple Cre e k and Kal
i
or
l
much
of
it
e
xists
combined
wi
t
h
te
llurium
e
o
g
I n the port i ons of the veins that hav e been subj e c t to the
oxid i sing in fl u e n c e s of surfac e wat e rs gold occu rs in a fr ee milling
c o 11dit ion
tha t is to say it unit e s r e adily wi th m e rcury t o form
1
amalgam being fr e e from t ellurium and bas e sulphid e s
Below th e r e ach of oxidising in fl u e n c e s th e gold is oft e n
associated with m e tall i c sulphid e s g e nerally i ron pyrites in which
it oft e n e xists entangled in an excessiv e ly fi n e condi ti on so fi n e
that wh e n the recov e ry of the gold is att e mpted by ch e mical
dissolution with a qu e ous sol u tions of potassium cyanide s u ffic ie n t
e xtrac t ions can only b e obtained wh e n th e sulphides hav e b e en
groun d e xtrem e ly fi n e so as to e nabl e e ach particl e of gold to co m e
in contact with the solvent
The Waih i bullion extract e d by th e cyanid e proc e ss from th e
M artha Hill lodes contains from on e quart er t o on e third per cent
o f selenium and on som e occasions as much as 1 p e r c e n t
bu t
no trace of this rare m e tal can be det e cted i n th e or e itself by
chemical te sts
S ilv e r or e is generally convert e d in the upp e r part of lodes into
the free—m i lling chloride which below water lev e l is displaced by
sulphides N ative silver bromid e s a n d iodide often accompany
the chloride
The sulphides of copp e r lodes ar e conv e rted in th e upp e r portion
of the vein into sooty secondary sulphid e s ox i d e s a n d carbona tes
often of great richn e ss A t th e outcrop t h e copper cont e nts have
been oxidised and remove d leav i ng rus ty brown caps of ironstone
mor e or l e ss quartzose and porous
—
Som et imes th e m e tallic
P o s itio n o f Va lu a b l e C o nt e nts
contents of a vein are evenly d i str i buted throughou t the gangue
b u r e tte d
,
.
,
,
.
.
,
,
,
,
,
.
.
,
.
-
,
-
,
.
,
,
,
,
,
,
,
.
-
-
,
.
.
,
.
-
,
.
,
,
,
,
.
,
,
,
.
,
.
.
.
1
parti e
p rti e
t h e p e io
a
t
e e be e t t go
t tt e e o i be e
i
o t t it
e
to obt i
et
o o
g
ee
ex i t i
b i ging th
eq te e overy o f
I t m u s al way s b e r m m r d h a
ld m ay b e fr a n d y e t
h a h r is c n s de ra l m c h an c a l diffi c u l ty in r n
cl s s o fi n e
cl s in c n a c w h th e m rc ury s o a s
ua
rc
a n a n ad
r c u s m al in th e f rm f am al am
.
s
n
e
OR E VEI
NS
71
.
G e nerally ho w ever t h e y occur mor e a t on e po i n t t han anoth e r
ex i s ti ng i n m a sses known as bu n ch es n es ts c h im ney sh oots p ip e s
,
,
,
-
,
,
,
,
or bon a nzas
O nly i n rare cases do v e ins carry payabl e valu e s for t h e ir whol e
lengt h or i n th e ir full w i dth from wall to wall Henc e a pay
shoot may be de fin e d as t ha t por ti on of an or e body wh i ch is
comm e rc i ally valuabl e
Th e majo rity of pay shoo t s dip in t h e sam e dir e ction as t h e
lod e s bu t g e n e rally at a fl a tt e f or s tee p e r angl e mor e often th e
la t ter H e nc e t he pay shoo t is no t always co e x te n s ive wi t h th e
lod e a n d often pas s e s ou t in d e pth
N arrow v e rt i cal or n e arly ver ti cal payabl e po rtions of a v e in
ar e te rmed c h imne ys or p ip es 5 and fl a t n e arly horizonta l por ti ons
c ou r ses or ben ch e s
The caus e s which hav e brought abou t th e unequal dis t rib u t ion
of t h e valuabl e con tents of a lod e i n shoo ts pock ets or cours e s
ar e eith e r no t known or bu t imp e rfec tly unde rstoo d It has
how e v e r b e e n no te d tha t gol d beari ng v ei ns b e com e e n riched a t
th e int e rs e c t ion of i nd i ca to r beds a n d fl in ty cro s s cours e s 5 and
tha t veins traversing propyl it ised andes i te becom e e nrich ed or
impo verished wi t h a s l i gh t chang e in th e charac t er of the ande site
Th e conn e ct i on of c i rcumstanc e s in thes e cas e s i s manifest but
t he exp lanation is diffi c u lt
—
Th e s e may b e of any s hap e a nd size Th e y
P a y S h oo t s
may d i p in th e sa m e dir e c ti on as the lod e and ye t b e inclin e d i n
lin e ar e xtension
cour se s ,
t
h
a
c
es
,
p
,
o
t
c
k
e
s
p
.
,
,
.
-
.
-
,
,
-
-
.
.
,
,
,
,
,
,
,
.
,
,
,
.
,
-
,
-
.
,
.
.
.
,
.
FI
G
.
4 2 — L on gitu di n al S ec t io n
.
( )
a
P a y -s
o f Vei
h oot
s
.
owi g
e io n o f p
Poor gro n d
n , sh
( b)
n
suc c
u
ss
a y -s h
oot
s
.
.
Pay shoots vary from a f e w yards to t housands of feet i n
leng th and som eti m e s t wo or mor e shoo t s occur i n th e cours e of
a v ei n s e parated by long e r or sho rte r str et ch e s of poor or e as
shown in fig 4 2
The d i p and p i tch of a pay sh oot sho ul d always be carefully
noted so as to ob ta in a clu e as t o the probabl e pos i ti on of th e
valuable or e a t d i ff e rent l e v e ls
I n many v e ins t h e payabl e mat e rial do e s not always extend
-
,
,
,
.
.
-
.
,
MIN I N G G
72
E OL OG Y
.
from wall t o wall The valu e s s om e tim e s li e on th e foot wall and
sometim e s on t h e hanging wall or i n a band of o r e situate d n e ar
th e c e ntre of th e vein or i n a th i n s t r e ak which crosses th e v ei n
obl i quely passing from wall to wall
The ext e nt of the payable ore can always b e a s certained by
syst e matic sampling provi ded a ca r eful r e cord is mad e of th e
values on th e m i ne assay plan
—
G o l d B o na nz a s
The rich bonanzas for which th e Tham e s
and Coromandel g oldfie lds are c e l e brated o c cur in th e richer z on e s
T h ey are places where the quartz contains coars e daubs or mass e s
of gold forming wha t is lo ca lly call e d p icke d or sp e c im e n ston e
wh i ch i s frequ e ntly found to yield as much as six ounc e s of gol d
to t he pound of ston e
Th e Hauraki bonanza vari e d from 1 00 to 1 2 0 f e et wide and
ext e nd e d to th e 300 f eet level from a poin t about 60 fe e t from
the surface It pitched sl i ghtly to the nort h e ast and was cut
o ff by a fault abou t 30 f ee t from Bunk e r s boundary
I n t h e se g oldfie lds t he pay shoots commonly occur along t h e lin e
of int e rsect i on of a cross v e in or fl inty wh i ch is a thin indicator
v ei n consist i ng of dense fl in ty quartz g e nerally pyrit i c
—
l
M
o
V
F aulting has tak e n place along
Wa l
e in s
v e m e n ts O i
the course of most larg e veins I n som e cases the faul t ing took
place before the fi llin g of th e fi ss u r e and i n o ther cas e s when th e
veins were partially formed but not consoli dat e d
When th e faulting t ook pla c e after the consoli dation of the lode
matter th e r e sult was the pro duction by attriti on of a lay e r of
pug or clay 0 11 th e wall 0 11 which th e movement took place O n
the sid e on which th e pug occurs all th e small v e ins and dropp e rs
are thus cut o ff or displac e d 5 and it is for this reason that branch
ing veins are only fo und on t he sid e on which no movem e nt has
tak e n place
I n some classes of country faul t ing along the cours e of a vein
has caused the formation of friction breccias on one or bo t h walls
S uch breccias seldom e xce e d a f e w feet in t h i ckn e ss a n d mos tly
form le n ticular shaped mass e s of varying l e ng t h and de pth
I n hard country movem e n t on th e walls has oft e n produced
sl i ck e n sides 5 and in som e cases th e fl u ca n or clay partings b e tw ee n
t h e vein matter and walls has assum e d a fl a ky or platy charact e r
t hrough the str e ss of lat e ral pr e ssure
O bs e rva ti on in many countries
I n fl u e n c e O f C o u nt ry -R 0 c k
h as shown that t h e valuable cont e nts of a ve i n are oft e n in fl u e n ce d
by th e character of the country rock trav e rs e d by th e vein I t i s
also recognis e d that ce rtain rocks favour the occurr e nc e of
par t icular or e s a n d min e rals Thus tin has a pr e f e r e nc e for
gran it e rocks 5 whil e copp e r is usually associated w i th serpentines
-
,
.
-
,
,
.
,
,
-
.
.
.
,
,
.
,
,
.
’
.
-
-
,
,
.
.
.
,
,
,
.
,
.
.
-
.
,
-
.
,
-
-
.
-
.
-
.
.
,
O RE VEIN S
73
.
diori te s chlori t ic schists and slates L i meston e mor e especiall y
wh e n dolom iti c y ie ld s lead i n many coun t ri e s I n Ch i li a n d
A us t r ia lia i t y ie l ds lead a n d s i lv e r ; i n Belgi u m z i nc 5 and i n
E nglan d iron a n d l e ad
A chang e i n t h e roc k of t en causes a chang e in th e richn e ss of
a vein
I n th e Hauraki g oldfie lds and in Tra n sylvania the veins are
produc t ive in al ter e d and es i t e bu t barren in the br e cc i as a n d
A t Cr i ppl e Cre e k t he v ei ns a r e m os t productiv e in and e s i t i c
tu fis
breccias
I n Y orksh i r e t he l e ad vei n s are good in limestone not so good in
grit and lim e stone wo rse in shale and l i m e ston e and wo rst in shal e
S a n db e rg e r strongly urged th e in fl u e n c e of coun t ry rock upon
th e con ten ts of v e ins 5 and his rese arches have be e n su pplemen t ed
and v e rifi ed in la te r y e a rs by those of many accomplish ed Am e rican
g e ologists whos e oppo rtuni t i e s for obs e rva ti on in th e fi e ld hav e
been w i de a n d varied
I n t h e H au rak i g oldfie lds th e au thor found that th e productiv e
cha ra cter of th e v e ins was s trongly in fl u e n c ed by the containing
rocks The r e sults of h is res ea rch e s in this r e gion du ring a period
of tw e lv e yea rs may b e s ummaris e d as foll ows z
i
s
Th
e
rock
which
has
y
ie
lded
t
h
e
largest
quan
t
i
t
y
of
gold
a
( )
a m od e ra tely ha rd y e llow i sh gray alte red an de si te t h e
k i n dly san dston e of t h e min e rs
b
o s t favourabl e country is not too sof t nor y e t too ha id
Th
e
m
( )
be i ng s hoo ti ng ground requi ring two or thre e shots to th e
shif t
0
I
v
e
ry
hard
country
rock
t
h
e
v
e
ins
ar
e
g
e
n
e
rally
small
e
r
n
( )
than i n soft roc k 5 and wh e n a v e in passes in to hard
and e si te it invariably becomes smaller a n d of t en th i ns
”
out to a m e r e clay pa rting or clay h ea d
d
Th
e
v
e
ins
in
the
ha
rock
hav
e
not
prov
e
d
so
remunera
r
d
)
(
”
“
tiv e as those i n the miner s kindly sa ndston e and this
i s du e not so much to t heir leann e ss as to th e ir small e r
siz e and the grea te r cost of working t h e m
e
( ) When a v e in pass e s from alte red and e s it e in to a tu fi or
br e cc i a i t in variably becomes barr e n or too low grad e
to b e payable This i s true in a ll pa r ts of the Hauraki
P e n i n s ula 5 and e xp e r ience has shown tha t the v e ins
which e xis t in t u fi s or br e ccias ar e of te n s u pe rfi c ia l i n
charac ter and s e ldom reliable as gold produc e r s al though
som e have been found to conta i n small shoo t s of a pa y
1
able natur e
1
J Park T h e G eol ogy a nd Vei n s o f Hau raki G old fie lds N Z
T r a ns
,
,
.
,
.
,
,
.
,
.
,
,
'
.
,
.
-
,
,
.
,
,
-
,
.
,
.
-
,
.
,
,
,
.
-
,
,
,
-
-
.
~
’
,
.
‘
,
,
.
'
-
,
,
.
,
N
Z
.
I
n s t.
,
lf im n g E n g i n e e r s ,
'
i
v ol
.
i 1 8 97 , p 4 6,
.
.
.
.
,
.
74
MI N
IN G G EOLOG Y
.
Th e m i ning op e rations of t h e past
—
th i r ty fi v e years in th e Hauraki ar e a have shown t hat in the
d i ff e rent belts of alt e r e d an de s i te th e r e ar e certa i n zon e s wh i ch
ar e mor e productiv e than o t h e rs E v e n in th e cas e of several
parall e l v ei ns i t has be e n found that all becom e e nrich e d on
e nt e ring the favourable zone t her e by a ff ording a graphic i llustra
t ion of t h e min e r s aphorism ore a g a inst ore
Th e re ar e several such zones in the M oa n a ta ia ri end of th e
Thames fi e ld th e best known being those at Ku ra n u i Hill and
Po i nt Russell T h e latt e r a ffords p e rhaps th e most graph i c
ill u stra t ion of th e in fl u e n c e of favourabl e country A t that
plac e the M oa n a ta ia r i mine is traversed by four large parall e l
lod e s— nam e ly th e D aun tl e ss R e ub e n Parr G ol de n Ag e and
Waiotah i all pursuing a N N E
cours e
O n en te ring t h e productive zone th e ore chang e s from e x
c e s s iv e l
low
grade
t
o
h
i
gh
grad
t
hi
character
b
e
ing
maintained
s
e
y
ti l l t h e zone i s pass e d through This zon e crosses t h e course of
1
th e lod e s n e arly at right angl e s
The following d i agram shows the general d i stribution of the
productive zones on this fi e ld
P ro du c t iv e
Z one s
-
.
.
,
,
’
-
,
-
.
-
,
.
,
,
.
,
,
,
.
.
,
.
,
.
,
,
.
.
FI G
(a h )
( bb)
( cc )
( cl )
o f N o th ern Po rtion f T hame G ldfi ld N Z
t i i f lt
G r at M
9v i
( ) N
Poi t R ell pro d ti e zo e
( f ) C ledo i vei
i pro d ti ve zo e o f l tered a de ite
K
( g ) W io t h i vei
S h oto v r vei
.
43
-
.
Pl
an
r
oa n a a a r
e
n
u ss
n
o
e
n
v
n
uc
e
s
au
uc
ur a n u
o
e
o
e n
.
n a
a
.
n
a
s
a
.
,
a
.
.
.
n.
n
.
.
M ining opera t ions disclosed th e circumstanc e that th e rich
zones w e re not only limited in wid th but also in d e pth F urth e r
th e y w e re found to dip to the southward t hat is in t he opposi te
dir e ction to th e dip of t he veins
The cross s e ct i on along the l i n e j oining c c shows th e r e lation
of th e parall e l v ei ns to t h e K u r a n u i pro duc ti ve zon e
The shade d portion repr e s e nts t he Ku ra n u i productiv e zon e of
alt e r e d andesite
J P rk Z
it p 5 0
.
,
,
.
-
.
.
1
.
a
,
oo. c
,
.
.
,
76
MININ G GEOLOGY
.
bl e nd e gal e na r e algar st i bn ite and calcit e show a marked
t e ndency t o aggr e gat e t h e ms e lv e s in horizontal zones in th e
1
orde r named
2
R i ckard m e ntions th e ord e rly distribution of ores in Colorado
W ee d stat e s that i n th e Castl e M ountain district in M ontana th e
ord e r appears to be gal e na on top passing i nto h i ghly zinc i f e rous
3
ores b e low and th e s e i nto low grad e pyr it e
A t Brok e n Hill l e ad and silv e r min e s in N ew South Wal e s
th e gen e ral distribution of ores in v e rt i cal depth has b ee n as
follows :
a
xidised
or
e
s
of
l
e
ad
and
silv
e
r
O
( )
G alena with bl e nd e
c
Blende
with
galena
( )
r h ot it e ,
,
,
,
,
.
.
,
,
,
-
,
.
,
,
.
.
,
,
.
W ee d in a pap e r on O r e D e pos it ion and V ein E nr i chm e nt
by Ascend i ng Hot Waters app e ars to support the hypoth e s i s
which assumes t hat t h e d i s tribu ti on of ores in hori z ontal zon e s is
th e r e sult of primary conc e ntra t ion by ascend i ng hot solutions
This vi e w has much to commend it
Th e e rupt i on of ign e ous magmas is of te n succ e ed e d by int e ns e
solfataric act i on of wh i ch notable e xamples are found in t h e
Y e llowston e Park in t h e Unit e d Stat e s a n d in the volcanic r e g i on
of th e N or t h I sland of Ne w Zealan d
Th e asc e nd i ng waters slowly circulating in contact with h e ated
rocks b e low b e com e sup e rh e at e d and in their upward cours e d i s
solv e vari ous substanc e s wh i ch th e y carry with th e m along th e
line o f leas t resis tanc e that is t owards th e hot spring pipe or
vent
M any substances insolubl e in normal con di tions are r e nd e r e d
e asily soluble in the pr e s e nc e of h e at and pressur e Th e un de r
ground wat e rs will therefore possess their gr e at e st solvent pow e r
wh e r e the gr e atest h e at and pr e ssur e preva i l wh i ch w i ll naturally
be at th e great e st de pth
W i th loss of hea t and pressur e the l e as t soluble substanc e s
will be pr e cip it at e d— tha t i s those substanc e s whos e dissolu t ion
was eff e ct e d un de r e x t r e m e h e a t a n d pr e ssure
As the wat e rs asc e nd t h e y w i ll con ti nu e to los e h e at a n d b e
r e liev e d of pressur e wi t h th e resul t tha t th e d i ssolv e d m i n e rals
w i ll b e pr e c i pita te d i n th e inv e rs e order of th ei r solub i l ity
When th e hot wat e rs r e ach th e surface the only subs tanc e s i n
solution in most cas e s will b e the extr e m e ly solubl e alkal i n e
1
“
“
,
,
.
.
,
,
,
.
,
,
,
,
‘
.
,
,
.
,
,
,
.
,
,
.
,
,
1
.
2
3
1
"
p
ik
J H S u rr, loc c it , p 8 4 1
A R c ard, T r a n s I ns t M in a n d M e t , L n d n , v ol Vi
d a nd P irs s on , B u l le ti n 1 39, U S C eol S u r ve y , 1 896
W H
e d, T r a ns A me r I n s t M E , v ol xxx
1 90 3
,
J
Wee
.
.
.
.
We
.
.
.
.
.
.
.
.
.
.
o o
.
.
.
.
.
.
.
iii
.
.
.
.
.
,
1 8 99, p 1 96
.
.
O RE V E
IN S
77
.
sulphat e s carbonates and silicates I n support of this i t may be
ment ioned that hot spr i ngs commonly deposit silica and rarely
m etallic s ul phides a t th e surface
I n many lod e s it is a common f e atur e to fi nd sulphi des or t h e ir
ox i dised produc t s a t the surface but in such cases it i s always
well to bear i n min d that veins wh i ch ou tc rop a t t h e surfac e may
hav e been t runca te d t o a gr ea te r or l e ss d e gr ee by d e nuda t ion
Th e obvious i nferenc e to b e d rawn from th i s proc e ss of ve in
fillin g is that impov e rishm e n t hi t h e or e mus t ta k e plac e i n all
v e ins at grea t d e p t hs du e to th e migra t ion of th e valuable
minerals from t he zo ne of dis so lu tion b e low to t h e zone of p r ec ip ita
tion abov e
—
I t h as be e n not e d in all
S e c o n da ry E n ric h m e n t O f V e in s
parts of the globe that r i ch masses of or e ofte n oc cur in t h e
ox i dise d por ti on of the or e b ody or in t ha t po rti on ly i ng n ear
water l e vel
M icroscopic invest i ga t ion has shown tha t t h e s e r i ch mass e s are
not of primary but of s e condary origin Th e ir g e nes i s is supposed
to be due t o the m i gra t ion of t h e valuable me tallic con t en t s from
t he higher pa rt of t he ve i n t o the lower pa rt of t h e oxidised zone
by the agency of meteoric wa t ers
I n some cas e s the process e s of d i ss olut i on mig ra ti on and
red epos i tion may have taken pl ace over and ov e r again each cycle
resulting i n an i ncr e as i ng d e gr e e of concentra ti on
The veins in which secondary enr i chm e n t ar e mos t ofte n s e en
are thos e of gold s ilver copp e r lea d and zinc
G old ores in t he zone of wea ther in g are ofte n augm e nted in
value by the long con ti nued disintegr a t ion of the v e in and the e n
closing rock thus perm i tting the gold s e t free from its matrix t o
conc e ntrate at the outcrop
E xtensive areas of th e Aus t ralian contin e nt have be e n subj ect
to sub ae r i al d enuda ti on sinc e the close of t he Pal aeo zoic p e r i od
and it is doub tl e ss du e to this caus e that so many no tabl e exampl e s
of mech a nica l enrich m en t of gol d bearing veins have b e en found i n
V ictoria and West e rn Austral i a
Th e m i gr ation of gold copp e r s i lver lead and zinc from t h e
upper to t he lower par ts of t he ve i ns i s affe ct e d by d e sc e nd i ng
surf ace wat e rs in t h e zone of vadose circula t ion The processes
involv e d i n t h e m i gra t ion are ( a ) chemi c al dissolut i on and ( b)
e lec t ro ch e mical deposi t ion
Ch e mical proc e ss e s may op e rate in various ways t o ca us e
secondary e nr i chmen t as follows
,
,
.
.
,
,
,
.
,
.
.
-
,
-
.
.
.
,
,
,
,
.
,
,
,
,
,
.
,
-
,
.
-
,
-
.
,
,
,
,
.
,
-
.
,
t he r e moval of wor thl e ss me ta l s t h e r e b y l eaving t h e
valuable cont e n t s i n a pur e r form
1
B
( ) y
,
.
78
MININ G GEOLOGY
.
r e moval of worthless metals and their replacements by
valuable m e tals remov e d from a high e r par t of the vein
3
d
e
position
of
valuable
m
e
tals
on
primary
sulph
i
d
e
s
in
B
( ) y
thos e por t i ons of the ve i n subj e c t to the in fl u e n c e of
circulating surface waters I n t h i s case th e primary
sulphides may form th e nuclei for the d e posit of th e
s e condary sulph i des
M anife s tly the fi rs t op e ration in the proc e ss of s e condary e n
r ic h m e n t is the ch e mical w ea t h e r i ng and oxidat i on of th e m etall i c
cont e n t s of the v e in i n the Katamorphic zon e
Th e ox i dation of bas e sulphid e s can b e s ee n in op e ration e v e ry
day I n a mass of mixed sulphides of iron copp e r z i nc and
galena th e iron will be the fi rs t to be a ffecte d from i t s a ffi n ity for
oxygen
I ron pyrit e s is decompose d and forms ferrous sulphat e which is
changed into Fe ( O H) 3 Fe 2 ( S O4 )2 and H2 S O4 The
attack s
mor e iro n sulph i de and forms ferrous sulphate liberating 112 8
wh i ch at onc e comb i n e s with free oxyg e n to form H2 8 0 4
The ferrous sulphate changes to the ferri c sulphate which attack s
gold and sulphid e s of copp e r lead zinc and silver The process
of dissolution must n e c e ssarily be slo w on accoun t of the extreme
dilution of t h e solutions
F or many y e ars i t was beli e v e d that th e only secondary enrich
ment that could take place was th e formation of rich bonanzas of
carbonate or e s and chloride of silver in th e zone above water level
But careful inv e s t igation in later years has shown that primary
sulphides have b e en e nriched by th e d e posit i on of secondary
sulph i d e s even in places below pr e sent water l e vel
1
I t was prov e d e xp e rimentally by Sk e y in 18 70 and c on fi r m e d
2
by L iversidg e in 1893 t hat gold is mor e read i ly prec i p i tat e d
from its solut i ons by metallic sulphides than by organ i c matt e r
F ur t h e rmore Skey show e d that sulphides of the base m e tals w e re
readily pr e c i pitated from alkaline sulphide solutions in a solid
coh e rent form in t he presen c e of iron pyri t es galena blend e
stibnite etc
Th e descend i ng acid solutions form e d in th e zone of oxida t ion
will attack th e constitu e nts of th e rocks through which they per
colat e with the production of alkaline silicat e s and sulphid e s
G ol d dissolved by ferric sulphate would b e also carried down
and d e posi t ed as l e af scale or wire gold in cracks i n sulphide ore
th e r e by caus i ng local e nrichm e nt
It is main t a i ned by some writers that secondary sulphides have
2
B
( ) y
.
,
.
,
.
.
.
,
,
,
,
.
,
,
,
.
,
,
.
,
,
,
,
.
,
.
-
.
,
-
.
,
,
.
,
,
,
,
,
.
.
,
,
,
.
1
W
ke
Pro e o
.
2
2
8
7
p
.
.
r a ns
S
T
N
,
y
f s s r L v rs d
.
ew
i e i ge
,
P
Z
ea l a n d
r oc
.
R oy
I
.
ns t
.
S
,
oc .
v ol
iii
1 8 70 , p 22 6
N e w S ou th Wa les , v ol xx v 11
.
.
,
.
.
.
.
,
1 893,
I
O R E VE N s
79
.
b e en formed below water l e v e l The ev i d e nce on th i s qu e stion is
not qu it e conclusive I n some cas e s chang e s of wa te r l e v e l may
have ta k e n place sinc e the secondary s u lph i d e s w e r e de pos ite d
1
2
Th e researches of E mmons W e e d a n d o th e rs have thrown
much l i gh t on th e s e condary enr i chm e nt o f v e in d e po s its bu t much
s t ill r ema i ns to be don e before safe g e n e ral i sa ti ons can b e form e d
Som e ve i ns through mov e ment of th e wall s hav e b e en sha tte red
to som e e xt e n t a n d r e c e men ted by m i n e ralis e d w a ters Such
wa t ers asc e nding through t h e crush e d 1 ei n ma t te r woul d d e pos i t
th ei r m e tall i c con te nts as sulphide s t hrough t h e re ac ti on of
pr i mary sulph i des conta in e d 1n t h e or e
I n t his way a s e condary concentra t ion of primary sul ph i des
may be eff ected by ascending wate rs
-
.
-
.
.
,
,
,
.
,
,
.
-
.
,
.
T h e A bsorp tion of M e tal s by C l a y s in R e l a tion to S e c ond a r y
E n mch men t — 1t of ten happ e ns tha t t he or e in t he zon e of
s e condary e nrichm e nt is associa te d wi th , or con t a i n e d in , a ma t rix
Of
cons i s ti ng of clay or oth e r fi n e ly di v i de d m i neral ma tte r
'
.
.
th i s th e r e ar e no mor e cha ract e r i stic examples than th e Kaol i n
silv e r ores of Brok e n Hill and the talcose gold or e s of Kalgoorl ie
Clay a n d clay e y ma t ter ar e t h e natural produc t s of t h e a lte ra
t ion of rocks and ores i n t h e zon e of Katamorphism
Th e i r
pres e nce calls for no comm e n t ; bu t th e fr e qu e nt occurr e nc e of
rich or e s i n a clay e y ma t rix in certain lodes has led t o much
spe cula t ion as to t h e r e la t ion existing betwe e n th e clay and its
m e tallic con t ents
I t has b ee n sugg e st e d by som e wri te rs t hat the a s socia t ion is
not acc i d e n tal nor t h e resul t of parag e n e s i s bu t du e to som e
absorp ti v e quali ty of the clay Tha t clay and fi n e ly d i v i de d
ma t ter poss e ss t he prop e r ty of abs o rb i ng or e x t rac ti ng m eta l s
from th e ir a qu e ous solutions has long b e en known a nd wi t h t h i s
knowledg e i n mind i t has been contend e d t hat th e clay e y mat te r
ac t ing as a porous fi lt e r in th e lower part of the zone of ox i da ti on
t hat i s i n th e b e lt of cem e n ta t ion has absorbed t h e m etals from
t h e d e sc e nding solu t ions t h e r e by e ff e c t ing a concen t ra t ion of
the valuable conten t s
Ther e is much t o b e sa id in favour of this vi e w b u t it has st i ll
t o b e d e termin e d wh e th e r clay e y mat t er and c e r ta i n porous
substances ar e primary or m e rely con t ribu ti ng causes i n t h e
forma t ion of zon e s of s e condary e nr i chm e n t
3
Walt e r Harvey W ee d e arly i n 190 5 d e scr i bed some e xp e r i
.
.
.
,
.
,
,
,
,
.
,
,
.
,
1
2
S
W
.
H
.
A m I
.
3
o
Weed
F E mm
.
.
n st
W
.
.
H
.
M in ing J ou r
T r a ns A m I ns t M E
B u ll G e l S oc A na ,
ns ,
.
N
e
.
o
.
,
Weed
.
,
.
.
,
n
s
,
r
.
.
Ab orption i
w Y ork 2 3 d F b
“
.
e
.
O re
1 90 5
,
1 0
v ol
.
xxx 1 90 0
xi 1 900 p
1
.
.
.
,
Depo s ition
.
,
,
.
.
1 79 ;
a nd
T ra n s
T h e E n g i neer in g
.
a nd
80
MININ G GEOLOGY
.
ments on the absorptive property of clays e tc made by himself
and others in the laboratory of the U nited S tates G eological
Survey in Washington The results c on fir m e d the researches of
1
W S k e y made in 186 9 and of E Kohler in 1 90 3 Wh o found
that clays and porous substances such as gelatinous silica
carbonaceous and colloidal matter possess th e power of extrac t ing
metals from their dilute aqueou s solutions
2
I n 1 8 6 9 Skey prove d experimen tally that fin e ly pulveris e d
massive quartz rock crystal a n d s i lica possess the power of
e xtract i ng the ox i de of iron from its acetate solution He also
found that prepar e d silica especially manifests th i s prop e rty i f
ignited at a low temperature and besides takes oxides of copp e r
T h e mor e fi n e ly
and chromium fro m their acetate solutio n s
divid e d the silica the more apparent is the abso rption
I n 18 7 1 he found that wh e n a w e ak ammon i acal solution of
copper containing a little c aus t ic potash is pour e d upon a fi lte r
of S wedish paper (cell u los e ) the li quid which pass e s through th e
paper is quit e or n e arly colourless and the filt e r is found to have
3
r e tained all or nearly all of the copper of such solution
I n 1874 the same chemist showed that clay possesses the
property of absorbing and fi xin g natural petroleum i n su ch a way
as to form a subs tance resembling natural oil shale the oil being
4
chemically combined with the clay
S ke y s discovery that g e lati n ous silica and porous substances
possess the prope rty of absorbing metals from their solutions has
an impo rtant bearing upon th e ch e mistry of ore deposition in
veins and in se c ondary enrich m e nt
—
T A Rickard when
I m p ov e ris h m e nt o f Ve in s in D e p th
“
discussing Professor P os e p n y s classic paper 0 11 The G enesis of
”
O r e D eposits
states that the general non pe rsist e nce of ore in
5
depth is a fact capable of proof
He contends that sinc e h e at
and pressure are the two great factors which incr e as e the solubility
of mineral substan c es the de e p region will favour solut i on the
most wh i le the shallow zone will favour precipitation owing t o
t he decrease of heat a nd pressure
There i s much in favour of this c ontention Progressive poverty
,
.
,
.
,
.
,
.
,
,
,
.
,
,
,
.
,
.
.
,
,
,
,
,
.
,
-
,
.
’
-
.
.
.
,
.
’
-
,
.
,
,
,
.
.
Koh ler Z it ch if t f p kti h G l gi 1 903 p 4 9
W S key O th Ab orpti ve Propertie o f S i li a d it dire t Hy d
”
i c o ta t with Water
T
n
N w Z
l n d I n t Wel l ingt o n N Z
1 86 9
l ii p 15 1
W S key
Ab orption o f Copper” from its A mm oni l S ol tion b y
C ell l o e in pre e e o f C u ti Pot h T
N w Z
l nd I n t
l iv
1
E
.
,
2
.
n
vo
ra
sc
e
eo o
s
c,
s.
e
c
s
ea a
.
,
s
ra
,
.
.
an
.
s
,
c
“
.
s
,
a
s
as
c
,
r a ns
ea a
e
.
s
p 332 1 87 1
“
4
W S y, N
s on th e F rm a
n an d
ns
fT r
u
n
”
s m lar M n ra l s ,
T r a ns N ew Z ea la n d I ns t v ol v
1
8
874
3
7
,
p
5
T A R c ard,
G n s is f O re D
s s,
D tsm ss ion , p 1 90
.
,
.
i i
.
.
,
,
u
aca
s nc
s
.
.
.
,
.
3
u
ur
e
c
.
.
r
n
,
n
s
e
ke
i e
ik
ote
o
.
e e
o
tio
epo it
.
Co tit tio o
ii
.
.
.
o b nite
.
.
vo
.
.
a
.
.
,
an d
O R E VE IN S
81
.
in depth below a c e rtain depth must be the natu ral corollary of
th e g e neral law governin g the o rderly d i s t r i bution of ores in
horizontal zones through t he agency of as cending wate rs
I n some cas e s impoverishment i n d e pth i s dete rmi n e d by t he
prevail i ng geolog i cal conditions O re v e in s which ar e con fin e d
to a s i ngl e ov e rly i ng form ation often die out or becom e exhausted
on reach i ng the un de rlying rock
A notabl e e xample of th i s is affo rd ed by t he hydro t hermal
ve i ns of th e Tham e s Tapu Co romandel and Kuao t un u m in i ng
d i str i ct s in th e Hauraki m i n ing reg i on of N ew Zealand wh e re
the gol d bearing v ei ns are contain ed in al te red an des it es which
r e st on a h i ghly e rod ed surfa ce of L ower Me sozoic shales gr e y
wacke a n d ad i nole
M ining op e rations have in all cas e s shown that when the veins
wh i ch occur n ear the bo rde r s of the and e si te fl o ws r ea c h the
bas emen t rock th e y d i e out completely or end in small strings
which soon disapp e ar in depth
Th e pr i nciple of secondary en richmen t preclude s the c ont i nuance
of th e enri ched po rt i on of t he v e in downward in ve rt ical dis tance
When the valu e s of secondary enrichm ent are added t o ore
already of a payabl e quali ty t h e r e sul t is a rich shoot or bonanza 5
but when as often happens th e secondary values a re added to lean
or e then th e n e t r e s ul t is to rend e r the l e an ore j us t payable
Below th e zone of enrichment th e lean ore will be u n p ro fita b le
Thus secondary en richmen t is a concen tration o f values in
th e oxidised or Kata mo rphi c zone due to t h e tra n fe re n c e of th e
valuabl e con tents from a high e r to a lower l e v e l by the fl o w of
mete oric waters O nly in rare c ases w ill prima ry s u lphid e s b e
enriched by t his ag e ncy
1
Th e Mi ning Comm i ssioners of V i c tori a includ i ng the late
Profe ssor M Coy and M r Alfred S e lwyn t h e S tate g e ologist
r e ported in 1 85 7 t hat e xper ie nc e in e v e ry country h ad p roved
t hat th e yield of gold decreased wi th the depth afte r a ce rta in
small lim i t was reached
1
Th e conclusion of the Commi s s i on e rs was in unison wi t h the
O pinion alr e ady expressed by S ir Ro derick M ur ch i s on i n th e fi rs t
2
ed it ion of his S itu ma This distingu i shed g e olog i s t a s th e
resul t of f urt her knowledge was induc e d to ma te r i ally mod i fy h i s
v ie w par t icularly h e tells u s as r e spec t s t he colony of V ic tor i a 5
bu t he still adher e d to t he belief t hat in g e neral gold ve i ns
2
d i m i nish in value as they d e scend
.
,
,
~
.
.
-
,
,
,
,
,
-
,
,
,
.
,
,
,
.
.
,
,
,
,
.
,
.
.
.
,
‘
,
,
.
’
.
,
,
,
,
,
.
1
th e
2
3
R e po r t to S u r v eyor C e ne ra l
Co l on y of Victor i a , 1 85 6 -5 7
S ir R d c I m p e y M u c h
L oc c it , p 4 96
a nd
-
o eri k
.
.
.
.
r i s on
.
Ch ief S ec re ta ry
,
S i ln r ta ,
th i
nd
o n the
editio
n,
M in in g R es o
1 85 9, p
.
f
ur ce s o
4 94
.
82
MINI N
GEOLOGY
G
.
The discovery of payable gold in a saddle reef in the N ew
Ch u m Rail way M ine at B e ndigo at a d e pth of 4 15 6 feet in
M arch 1 90 5 proves that the limit in depth assumed by M urc hiso n
must be exten de d t o a dept h probably not under 5 0 0 0 feet
I t i s now generally r e c ognised that a
I n dic a t o r B e ds
vein may become e n riched or impov e r i shed in passing from
one kind of rock to another
Thus lead veins which are
productiv e in limeston e are often poor in sandstone or shale 5
and gold v e ins payable in andesite are often barren in tufts or
breccias :
There are som e w e ll known cases wher e this in fl u e n ce is
e xhibited in a sp e cial an d notable man ner I n Kongsberg in
N orway the prevailing rocks are gneiss and c rystallin e sch i sts
C e rtain bands or zones of the latter are impregnated w i th fi n e ly
divid e d sulphides of iron copper zinc and oc c asionally o r es of
l e ad ni ck e l cobalt and s i lver
Thes e mineralised bands locally known as fa h lbands conform
to the strike and d i p of the enclosing gneiss and schist
The c ountry rock and fahlbands are inte rse c ted by silv e r bearing
veins and it is notorious that these veins ar e only productive
where they t ravers e th e fahlbands
T h e indicator beds of Ballarat in V ictoria have exercised a
remarkable in fl u e n ce upon the distribution of the gold in the
v e ins of that ar e a
Th e country—rocks are Silurian slates and sa ndstones which
are generally tilt e d at high angl e s and often approa c h t he
vertical position They ar e interb e dded with ce r tain thin seams
of black carbonaceous shale or slat e to which th e nam e indica tor s
is locally applied from the circums tance that wher e ver a qua rtz
v e in cross e s one of these shale seams it uniformly be c omes rich e r
a long th e plan e of inters e c tion
The most p e rsistent of the shale seams known as T h e I ndica tor
“
1
is describ e d by E L idg e y as a narrow bed of dark slat e
usually showing cleavage planes and con taining a large per
”
centage of pyrite distributed irregularly through it
I t varies
from a mere sheet to an inch thick and c an be tra c ed for a
d istance of 7 or 8 miles
I t is nearly vertical and is
int e rs e cted by a s e ries of nearly hori z ontal quartz s e ams which
2
ar e commonly enriched a t or in the vicinity of the indicator
D r Jack in his report on G ymp i e g oldfie ld in Qu e ensland
stat e s that t h e v e ins are richest i n c e rta i n bands oi black shale 5
-
,
,
,
.
-
.
,
.
,
,
,
-
.
,
.
,
,
,
,
,
,
,
.
,
,
.
-
-
,
.
-
,
,
.
,
,
.
,
,
-
,
.
-
,
,
,
.
,
,
.
,
,
.
-
,
,
.
,
,
,
,
-
1
E L idg e y , R ep or t
2
A
T
R c ard,
A m er ica n I n st
.
.
.
i tere ti g
n
s
n
ik
.
s u mm a
E a st C oldf te ld
T h e I n d ca r V n , B al lara
v ol
1 90 1 , p 1 0 94
Th
,
th e a va la l da a r la n
th e
on
ry o f
th e B
a lla r a t
.
i to ei
t A tralia T
xxx
i paper o t in
i b e t e ti g to
i di ator
us
,
.
.
.
.
c
s
n
c
r a n s.
,
s
,
n a
s an
84
MININ G
G
EOLOGY
a ra g e n e s is
P
.
.
I t has be e n shown by mining operations everywhere that
certa i n m i nerals and or e s are mor e frequently associated with
e ach other than with other minerals
The g e netic processes
wh i ch caus e d t he format i on or deposition of a certain mineral
oft e n Operated so as to cause the deposition of anoth e r mineral
.
,
or minerals at the sam e time and in the same pla c e
This parallel or synchrono u s genesis of ores and minerals
which has brought about a common association in the matrix is
known as p a r ag en esis and is probably governed by the laws of
chemical solution and pre c ipitation Substances soluble at th e
sam e t e mperature and pressure will pass out of solution together
i n the zone of decreas e d pressure or temp e rature The causes
which led to the constant association of certa in minerals su c h for
example as gold and quartz tin and wolfram are still very
obscure
The following table on the basis of that comp i led by V on Cotta
affords a clear V iew of the ores and mineral commonly asso c iated
in metalliferou s deposits
.
,
,
,
,
,
,
.
.
,
,
,
,
,
.
,
,
A SS O C I AT ED
e ber
T wo M m
G alena , b l en de
s
O RE S AN D M I N ER A L
ee Member
T hr
.
G alena
b lende
s
F o ur
.
i ro n
.
o r M ore Member
s.
e blende i ron p yrite
pyrites
q artz
Iron p yrite ch l Iro p yrite h l py Iro p yrite
h al op yrite
rite q artz
g lena b le de q rtz
py it
G o ld q rtz
G o ld
qu rtz
G o ld quartz i ro n p yrite
pyrite
b le de g lena r eni cal
p yrite
G ol d tel l ri m
G o l d te ll ri m q rtz G o ld tell ri m i ron pyrit
q rtz
Cob l t n d n i k l Cob l t d n ickel
Cob lt nd ni kel ore
ore
p yrrh otite
pyr h otite q artz
wo l fr m
T
w lf
wo l fram q rtz
t
Ti
Ti
q
to rm line
Ci b r
Ci b r i ron p yrite C i b r iro n py rite
p yrit
q artz
q rtz l p r
M g eti t
h l orite M g etite
h lorite
h lo r ite gar et
M g etite
pyroxene py rite
g r et
C h o m ite
C h ro mite erpenti e C h ro mite er penti e ol i i e
p
ti e
o l ivi ne
py o xene
,
,
,
G
al n a ,
u
,
s,
r
co
n
s,
e,
ua
,
a
u
,
,
a
s,
a
,
,
.
n
a co
c
n
,
,
,
u
,
u
,
u
,
ua
a
c
an
a
e
o1e s ,
s,
u
a
n -ore ,
,
o
u ar z
a
n na
,
es,
a
n
u
e, c
a
,
n
,
n
ser
s,
,
ua
n
en
,
a
,
n
.
s,
,
ca c s
,
a
.
c
,
,
r
,
.
n
,
ua
,
a
a
s,
u
,
n
s
n
,
s
,
s
es ,
,
c
,
,
,
c
,
a s
,
o re ,
nn a
,
a n
r
a
.
s,
a
u
nn a
u
r
ra a1 ,
ua
.
a
,
111-ore ,
,
.
,
ua
a
c
,
a
,
s
u
c
,
n
s,
,
s,
,
,
.
v n
,
,
.
I n a general way e xp e rience has shown that tin tungsten or e s
and gol d hav e a preferenc e for siliceous rocks ; and iron c h ro
m i um platinum nick e l and copper for basic rocks
,
,
,
,
,
,
.
,
O R E y am s
85
.
Un t il r e c e n t y e ars
i t was bel ie v e d by phys i c i sts t hat the i ncr e a se of te mp e ra t ur e
nam e ly 1 F ahr for ev e ry 6 0 fee t obs e rved in th e driving of t h e
Sain t G othard tunnel was th e normal rat e in all pa rts of t h e
crust of the ea rt h Thi s b e l ie f is n o w known to b e e rron e ous
O bservations tak e n i n d e ep m i n e s and bore holes in diffe r e nt par t s
of E urop e America and Aus tralia during t he past de cad e hav e
prov e d t hat
R oc k T
e m p e ra tu re s
in D e e p M in in g
—
.
,
°
,
,
.
,
.
.
-
,
,
,
,
o
Th
e
t
emp
e
rature
of
t
h
e
cr
u st i ncreas es with the d i stanc e
( )
from th e surfac e
That t h e ratio of i ncr e as e of temp e rature to d e p th t e t h e
temperatur e gradient is not the same in all places
That
t
he
t
emp
e
rature
gra
i
e
nt
is
not
uniform
for
all
d
e
p
t
hs
0
d
( )
e v e n in t he sam e plac e ; tha t is isog e oth e rms ar e no t
1
parall e l in the uppe r part of the crus t
d
That
t
he
temperatur
e
g
rad i ent incr e as e s with th e d e p t h
( )
I n the Comstock lod e which i s e nclosed in and e sit e s of middl e
T e rtiary dat e the temperatur e w as found to ris e 1 F ahr for
2
every 30 f ee t in d e p th
Th i s i ncr e a s e is e xc e p ti onal and
appar e ntly caus e d by a s t rong upwa rd fl o w of h e a te d wa te rs i n
th e v e in fi s s u r e s The g e olog i c condi ti ons sugg e s t t h e waning
phas e s of solfataric ac ti on as th e sourc e of th e h e a te d wa ters
A t t h e O haeawa i qu i cksilv e r m i n e s in N ew Z e alan d th e rock
t e mp e ratur e incr e ased so rapidly tha t boil i ng water was met w i th
at a dep t h of 2 0 0 fe e t from th e surface H e r e again w e ar e
man if e s tly d ealing with expir i ng volcanic heat Th e basa l t cap
of quite late T e rt ia ry dat e t he ho t springs and sinters sulphur
and cinnabar d e posits leav e lit tl e room for doubt in t h i s ins t anc e
Volcanoes whe th e r r e c e nt or Te rtiary ar e situa t e d in a h
parts of the crus t Som e parts how e ver a re
n o rmally ho t
abnormally cool F or in stanc e P rof e ssor Agassiz found in t h e
Calum e t and H e cla mine at L ake Supe rior a ris e of only 1
3
F ahr for e very 2 2 3 feet in d e pth
4
I n four gold mining centr e s in V ictoria t h e increase of
temperate was foun d to b e as follows
a
.
,
.
.
,
-
,
.
-
,
.
-
.
,
°
,
.
.
-
.
.
,
.
.
,
,
,
,
.
,
,
.
,
,
,
.
°
,
.
.
-
,
South M aldon M ine M aldon
1 F ah r for e v e ry 8 1 feet i n d e pth down to 1 700 feet
,
°
.
Pro fe or
e
ego
e pe t e
.
R e dmay n ,
U nd r r und T m ra ur s , S ou th S tafi or dsh ir e
a nd E as t Wor ces ters h i r e I ns t M in E ng , 190 4
“
2
m s c L d , Jlf onog rap h I I I ,
T h e G l y f th e
G F B c r,
a sh n t n
u r v ey ,
l
3
88
2
S
G
a
S
2
6
1
U
,
,
p
3
s e , A me r ic a n J ou r n a l of S c ien ce ,
v ol
r f ss r A
18 95, p 5 03
”
“
1
R c
H C J e n in s ,
T m ra ur s in V c r a, P r oc A us t A ss oc
A dv S e , v ol ix p 30 9, 1 90 2
1
ss
.
e ke
.
.
.
.
Poe o
.
iz
‘
.
.
.
.
.
.
o
.
.
'
.
.
eo og o
C o to k o e
W i go
i
o k e pe t e
i to i
.
.
.
.
.
.
.
.
.
86
MININ G GEOLOGY
.
South G a i d e n G ully Bendigo
1 F ahr for every 1 7 fe e t m depth do wn to 300 0 f ee t
Band and Albion Mi ne Ballarat
1 F ahr for e v e ry 80 f ee t in dep t h down to 2 0 80 fe e t
Ne w Chum Railway B e ndigo
1 F ahr for ev e ry 7 7 5 feet i n d e pth down to 3 6 4 5 fee t
Th e country rock l n each case is S ilu i ia n slate and sandston e
The following tabl e s of rock temperatures prepared by Professor
1
E ver e tt are of much i nt e r e st in c onn e ction with this que stion
,
°
.
.
,
°
.
.
,
°
.
.
-
.
-
.
,
T AB L E
I
—OB
.
S ERVAT I ON S O F T E M PER A T U RE
AN D V ER T I C AL B o a m e s
MI N
A T
ES
.
F e et
Depth
( feet )
pe r
D e ree o f
I mercas e
c
O
.
.
iei
P a ru s c h ow itz ( S l s a )
S c h lad a c h ( n ea r L i s c ) ,
re n e r
S
( n ar B rl n ) ,
s
h l n (
V r n a),
n dl
n ( n ar Man c h s
r) ,
,
eb
epi
pe b g e e i
W ee i g We t i gi i
Pe eto e
e te
Port J k o n
b idg ( e r Wig )
R
D ki fi l d ( M n h e ter)
A h to M o ( n ar M h
T m r k ( L ke S perio r )
S arle ( L i o l h i re )
Ki g woo d ( ne r Bri tol )
ac
os e
n
a
a ac
ss
n
s
T AB L E
e s te n
an c
a
s
,
,
e
nc
c
c
a
e
s
an
n a
e
r
n
u
s
u
,
ns
,
a
s
E THS
—D 1’
11
.
T A B L E I II
,
A T
WH I C H 10 0
—C A L C U L AT ED D EP T H S
.
WO U
L D
B E
FA H R
°
.
A T
FO U N D
.
F eet
.
R os e b ridg e ,
S carl ,
Kin g s w o od ,
D u kin fi e ld ,
h el n ,
sh
n M ss ,
e
344 9
34 69
3 6 72
37 2 2
4 1 92
W e i g
A to o
1
Pro fes or
Coa l S
s
u pp
J
lies ,
Lo
e ett
Ev r
,
nd n , 1 90 4
D
.
o
.
,
Ev ide nce bef or e
th e
Roy a l
Co mm iss ion
88
GEOLOG Y
MININ G
.
tur e it is r e markabl e how lit t l e trus t worthy info rma t ion has b ee n
record e d i n regard to progr e ss i v e und e rground t e mp e ra t ur e s e ven
i n plac e s wh e r e mining has b e en carr ie d on for g e nera t ions Th e
ti m e i s approaching when the recording of rock t e mp e ratur e s
must b e s yst e matically und e rtak e n in all d ee p m i nes
T e mperatures should b e noted w it h r e asonabl e skill and pr e
c is io n a t regular int e rvals both when sinking a n d d r i ving i n n e w
ground 5 and at all plac e s wher e ther e is a chang e of rock
O bserva t ions taken in a carel e ss or haphazard mann e r are of no
valu e a n d in som e cas e s may ev e n be worse than usel e ss as th ey
may l e ad to th e formation of e rron e ous conclusions
Th e pr e caut i ons to b e obs e rv e d in taking und e rground t e m
1
e ra tu r e s have been succinctly summarised by H C J e n kin s
as
p
follows
,
,
.
-
.
.
,
,
.
.
.
Temperatures should be taken in ne w g r ou nd that is i n th e
fac e or head i ng fr e shly brok e n wh e r e th e work is b e ing
—
rapidly pushed ahead Th e rock walls soon becom e
cool e d by v e n ti lating currents
2
Where
possibl
e
th
e
rock
should
b
e
free
from
sulphid
e
s
( )
easily oxidised since chemical r e actions a t t e nding ox i da
t ion are e xo t herm i c When sulphide s ar e pres e nt t he
t e mperature should b e tak e n at onc e
3
V
ery
w
e
t
ground
must
b
e
avoid
e
d
as
i
t
will
gen
e
rally
giv
e
( )
a lower r e ading than th e true on e s i nce t he water w i ll
in mo s t cases be descending surfac e wa te r O n th e
oth e r hand ascend i ng de e p—s e ated wat e r will t e nd t o
exaggerate th e temp e ratur e
4
ffi
After
drilling
s
u
c
i
e
n
t
t
i
m
e
must
be
giv
e
n
to
p
e
rm
i
t
th
e
)
(
abnormal h e at of drilling to diss i pat e its e lf befor e taking
a rock t e mperature A f e w minutes will generally s u ffi c e
for t his
5
Th
e
drill
hol
e
must
be
deep
e
nough
to
avoid
th
e
tempera
( )
tur e of the face of rock Agass i z used holes 10 f e et deep
I n th e maj ority of cases 6 f ee t holes are s u ffi c ie n t
6
( ) The bor e hol e s should be horizon t al by pref e rence
7
T
h
e
t e mp e ratures should b e tak e n with a high class clinical
( )
t hermometer graduated from say 80 t o 1 15 F ahr a n d
reading to 0 0 5 F ahr and corr e cted against a standard
thermom e ter Wh e n ins e r t e d in th e hole the t h e rmom e ter
should be wrapped round with three layers of fl a n n e l
L im its O f D e e p M in in g — M ining at great depths w i ll be
limi t ed by t h e underground temperature and economic considera
1
( )
,
,
,
.
.
,
.
.
,
,
-
.
,
.
,
-
.
.
-
.
.
.
-
.
-
°
,
,
°
,
.
°
.
,
.
,
.
.
1
H C
.
S
e
v ol
.
.
J
ix
e n kin s ,
.
R
o k T em perat re
c
p 30 9, 1 90 2
.
u
.
s
in
V i c tori a
,
P
r oc
.
A
u st
.
A
ssoc
.
A dv
.
O RE V
E I NS
89
.
t ion s B y t h e ad op tion of secon dary v e n ti la t ion a n d m et hods of
r e frig e ra ti on mining coul d doub tl e s s b e ca rr i ed on a t de p t hs
ranging up to 65 0 0 fe e t according to t h e local i ncr e men t of
temp e ra t u re
M e tas o m a tic R e p lac e m e n t — Unt i l lat e ly it wa commonly
b e l ie ved t ha t or e d e posi t s m e r e ly fille d pr e ex i s ti ng fi ss u r e s a n d
cavi tie s in coun t ry—rock I n r e c e nt y e ars write rs on or e forma ti on
hav e been incl i ned to plac e mor e or less s t ress on wha t has be e n
t ermed me tas om a tic r ep la ce men t
Accord i ng t o this it i s surmis e d tha t i n many cas e s a t l e as t no
previous caviti e s e x i sted but tha t t he waters p e rcola t ing thr ough
t h e rocks dis solved cer t a i n t ra cks or zon es which t h e y r e plac e d
wi t h or e mat ter and gangu e
This proc e s s of r e placem e nt is w e ll known to petrologists to
have tak e n plac e among t he constituents of many roek mass e s no
ma t te r how dens e includi ng all me tamo rphic rocks and all ol d er
i gn e o us and e rupt i v e mass e s
I t is known as metasomatism ( mean i ng chang e of body ) a n d is
du e to inte rnal ch e mical r e ac ti ons wh i ch s e e m to tak e plac e as
r eadily in rocks as do th e m e tabolic chang e s in liv i ng organ i sms
I n many cas es m i n e rals are replaced mol e cul e by molecul e
giving r i s e t o wha t i s te rm ed min e ral ps e udomorph i sm Bu t i n
t h e processes wh i ch a ff e ct chang e s i n rock mas s e s r e ac ti ons ar e
s e t up b et w e en t h e di ffer e n t cons t i t uen t m i nerals ther e by to
in g n e w min e rals capable of segr e ga t ing t hem s e lv e s i nto mass e s of
all siz e s
G n e iss and mica schist a r e famil i ar exampl e s of t he work of
segr e ga t ion and mol e cular r ea rrang e ment of t he domin ant con
s t itu e n ts of alt e r e d sedimentary rocks
Such altera t ion i s te rm e d
anamorph i sm and always ta kes plac e in the anamorph i c zone
Th e i nternal chang e s that affect eruptives ar e known to e v e ry
pe t rologist Bes i d e s t hese chang e s which are c h ie fl y mol e cular
rock masses and especially e rup ti v e rocks may b e so al te r e d by
th e a ct i on of c i rc u la t ing waters as to bear no r e s e mblanc e to t h e
.
.
s
-
-
-
.
’
.
,
,
,
,
-
.
-
,
,
,
.
,
,
.
,
.
-
,
,
.
-
.
.
,
,
.
-
,
,
o r iginal rock
Thus in many cases andesi t es have b e en chang e d to propyli te
by t h e removal of c e r tain e ssential consti t u e nts a n d the s u bs t i
t u tion of o t he rs
Rock r e plac e m e nt is doub tless pr e c ed e d by
alt e ration
2
1
M e tasomatic r e placem e nt as de fin e d by Van Hise and Emm ons
does not n e cessarily imply a mere subs t i t ut i on of mat ter mole
c ul e for mol e cul e as happens in the process of pseudomo rph i sm
which involves t he pr e servation of the o riginal form of t h e sub
1
V a n Hi se l 6th A n nu a l Rep o rt U S G eol S u rve y Part I
p 6 89
2
S F Emm o ns U S G ao l S u rve y M mzog r ap h " I I
5
65
p
.
.
.
,
,
,
,
,
.
.
.
.
,
,
.
.
.
,
.
.
,
.
,
.
.
,
.
.
90
MININ G GEOLOGY
.
stan c e replaced but an int e rchang e of substanc e th e dissolved
rock b e ing replac e d by gra i n s or cry s talli n e aggr e gat e s of on e or
,
nao r e nahne r a ls
,
.
That subs ti tution did howev e r take place in some kinds of
deposits is w e ll known I n t h e tin impregnat i ons in granit e
in N ew S outh Wales pseudomorphs of t i n oxide in the form of
orthoclas e are not uncommon 5 and many o t her examples coul d b e
quoted having r e ference principally to th e r e placement of isolated
crystals in crystallin e and eruptiv e ro c ks
Slow replac e men t of substan ce by a progressive movem e nt of
th e solu t ions in a de fin ite dir e ction must b e assum e d to have
tak e n place in the formation of or e deposits compos e d of massiv e
aggregates I n most cases the direction of movem e nt would be
determin e d by a rock fracture or line of fault
I n the case of deposits formed by de e p—circulating solutions it
is manifest that circulation could no t be rapid as the fac e or breast
wher e metasoma t ic process e s w e r e active would form a blind end
or cu l de s a c Whatever circulation ex i st e d would be du e to con
vection currents whi c h in deep —seated cavit i es could only b e
feeble
This now raises the question as to the transfer e nc e and supply
of dissolved matter to the continually advanc i ng fa c es of meta
somatic action
The energy which caused or at any rat e ac c elerated this trans
f e rence was probably osmotic pressure which has been shown by
van t Ho ff to be a for c e of great intensity
I t has b e en p rov e d that when a po rt ion of dissolved substanc e
i s deposited from a solution at any point the osmo t ic balanc e is
dis t urbed 5 and immed i a t ely more dissolved mat t er travels to that
point i n accordance with the well —e stablishe d laws of osmotic
di ff usion ther e by providing new matter to augm e nt the growing
mass of ore
Arrhenius and G ill e tte hav e urged the claims of osmo t ic
1
pressur e t o be consid e red a facto r in ore format i on
O smotic pressure is the ch e mical principl e which compels
solut i ons to maintain an equal state of concen t rat i on throughout
th e ir whole mass and since it is always called into being when
deposition commences its operation as an agency in vein fillin g
must have been assumed by writ e rs on th i s subj ect although
seldom s p e c ific ally m e ntioned
M etasomatism is a proc e ss of lode formation by replacement
an d does not concern itself with the source or origin of the
dissolved matte r contained in th e solutions
”
1
G illette
O sm osi s as a Fac tor in O re F ormatio n T r a ns A m I ns t M E
,
,
-
,
.
-
,
,
,
,
,
.
-
.
.
,
,
-
-
.
,
.
.
,
,
,
‘
.
,
,
.
-
.
,
-
,
,
.
-
,
.
,
1 903
.
,
.
.
.
.
,
92
MI N IN G G EOLOGY
.
for many v e ins but admit s that for many others — p e rhaps th e
maj ority of fi s s u re v e ins — th e r e se e m s to b e som e thing lacki n g in
this explanation
Vogt c la s s ifie s th e metasoma ti c process e s caused by the circula
1
t ion of or e solu tions as follows
,
-
.
-
( a ) Al t eration forming greisen cassit e ri te rock et c
,
,
b
S
c a ol itis a t io n
( )
p
.
.
( c ) Propylitisation
d
( ) Kaolinisation
.
.
( ) Sericitisation
(f ) Carbonatisat i on ( with dolomiti sation )
S
i
l
i
i
fi
i
a
c
c
t
on
(g )
h
Z
l
i
i
i
o
e
t
sa
t
on
( )
t
I
ntense
con
t
act
m
e
tamorphism
()
He agr e es with E mmons Beck e r L indgren and othe rs
m etasomatic replac e men t plays an important pa r t in the forma
tion of min e ral veins and ore bodi e s
I nformation w ith r e gard to vein structur e charac t er a n d in
fl u e n c e of wall rock should b e place d on record on all possibl e
occas i ons A p et rographical exam i na t ion of t h e vein ma tte r a n d
wall rock for som e d i stance on e ach s i de of t h e ore body will
oft e n t hrow much l i ght on the genes i s of t he or e 5 but care mus t
b e taken i n forming g e neral i sat i ons on microscopic e vidence alon e
e
.
.
.
.
.
,
-
,
-
.
-
,
,
-
-
.
-
-
.
1
Pro fe or V ogt
p 66 0
.
ss
.
“
,
Problem
s
in th e
G eo l ogy
of
O re
D epo s its
,
l oo
.
'
czt
.
,
IV
CH A P T ER
T H E DY NA M I C S O F L O D E S A N D B E D S
.
C ON T E N T S — D fi niti n o f F ults — F lt pa r ll l with B e l — D ip F lt
S t p F l t — T ro gh Faul ts — R le fo r In l ined L od — Z i mm er m nn
G rap h i M et h od
e
:
e
au
s
c
au
a
o
u
u
s
a
s
e
au
i
c
es
a
s
’
s
.
M in e ral beds and v ei n s may be ben t
or frac t ur ed e l e vat e d or depressed by t h e slow s e cular move
ments which build u p continental areas 5 or til te d and d i slocated
by th e sharper mov e ments propaga te d by the intr us i on of an
igneo us magma 5 that is th e d i sturbing agent s may be orog e n i c
D e fi n itio n
Of
F a u lts
—
.
,
,
,
or hypogenic
D i s locations wi t hout movem e nt of the rock on eith e r wall ar e
simple fractures 5 bu t in th e maj ority of cas e s t here has no t only
be e n fra cture but also displacemen t I n oth e r wo rds th e ren t s
have b e come faults
A faul t may be de fi n ed as a fractur e on on e s i de of which
movemen t has tak e n plac e whereby the roc ks on one s i de have
be e n displaced r e lativ e ly to thos e on t h e o ther sid e
F aults ar e ca us ed by c rust stresses Th e y run i n all direct i ons
but the maj or faults of a r e gion ofte n run in the same gen e ral
dir e c t ion
A faul t may run parallel with the cours e or strik e of a bed
or v e in 5 or cross t he c ou rse a t r i gh t angles or at any o t h e r angl e
F aults are no t often ve rtical bu t i ncl i n e to on e s i de or t h e
other A fault is said to hade wh e n it inclin e s from the ve rt i cal
plane The had e of a faul t is ther e for e t h e angl e which th e
fault makes w it h the v e rtica l plane
The had e—l i ne of a fa u l t i s the oblique resulta n t of t wo
pri ncipal component forces namely gravitat i onal s t ress ac ti ng
v e r t ically or rad ially towards the centre of the e arth and la t eral
t hrust ma inly du e to subs i d e nce
Faults ar e of two kinds namely
.
,
.
.
.
.
,
.
,
,
,
.
,
.
,
.
,
.
,
,
.
,
( )
b
( )
a
N or m a l f a u l ts
R e ve rs e d or o ver l ap
.
93
fa u lts
.
94
MININ G GEOLOGY
I n normal faults
the fault hades
th e downthrow
.
is towards th e side to which
.
FI G
.
45 — N
.
ormal
F a ul t
.
I n F ig 4 5 the hade of the fault and downthro w of th e beds a re
tow ards t he west
I n rev e rsed or overlap faults the downthrow is on the foot wall
sid e of the fractur e
.
.
-
.
FIG
46 — R
.
.
I n the above
thro w 0 11 the
ever ed o r O verl p Fa lt
fi g u r e , t he
foot wal l si de
-
.
a
u
.
hade is to the west
and
,
.
FI G
FI G
s
47 — R
.
.
48 — S h
.
ever ed or O verlap Fa lt
s
u
.
arp F o ldi n g with o u t F ract ure
.
Reversed faults are intimately connected with sharp
and synclinal fold i ng T h e stress e s i ntroduced by th
of beds are ofte n r elieved by faulting a n d shearing
.
.
the
96
MININ G GEOLOGY
.
The vertical line a h shows the vertical displa c e
m i n e rs d ownth r ow or up th r ow according as th e fault is
from th e e ast or west
,
.
FI G
.
52
.
— S h o wi ng D i s placements
by S
trike F
aul
t
.
The lin e c b shows the amount of horizontal displacement
d i sseverment whi c h is sometimes erroneously termed h e a ve
.
FI G
C ro
.
53 —
.
f Bed tr er ed b y S trike F lt
p rt P l
L o we p rt
o f Bed lo g li e A H h o wi g r p titio o f di lo cat d bed
1p pe r
1
s s -s ec tl o n
a
,
s a
an
n
o
s
n
av
,
s
s
n
au
e
e
n
r
.
s
e
‘
‘
a
s.
,
T HE
DYN A MI C S
OF L O D ES
A N D B
E DS
97
.
When a fault displ a ces s tra tified rocks th e lin e s of bedding
afford a measure of t h e vertical displac emen t 5 bu t in t h e absence
of bedding pla nes or some rock marked by a dis tinc t ive peculiari ty
of colour or compos i ti on th e r e is no c e rta in means of measuremen t
A str i ke fault ca uses no la te ral d ispl a cement of the beds wh i ch
i t inte rs e cts 5 but wh e n the beds ar e inclin ed i t may produce a
rep et i ti on of thc d i slocated b e ds as shown in fig 5 3
I n reg i ons which have been subj ect to long con t in ued denu da
t ion on e s i d e of a faulted seam may be en t irely r e moved as
shown i n fig 5 4 Th i s i s no t un common in th e cas e of young
S e condary a n d T e r t iary coal me a sures h angin g on t h e fl a n ks of
mounta i n cha i ns
,
-
,
.
-
,
,
,
.
.
-
,
,
.
.
-
.
FI G
.
54 — S
.
e tio o f N ormal Fault h o wi g
b y de
datio
c
n
,
n
s
nu
n
on e s
i de o f eam re mo ved
s
.
The s e am may be pa rt ly removed by d e nudat i on
both sides of th e faul t as indicat e d in figs 5 5 and 5 6
,
55 — Sec
.
tion
sh
n
e
a
on e or
.
.
owi g S am p rtly remo ved
o f F lt
0 11
on
i e al on g l in e
One S d
au
When a fault po ssesses t he sa m e dip and strik e as a seam or
min e ral v e in t ha t is when it conform s to t he bed din g pla n e s it
ca uses no apparent d i sturbance in the r e lat i on of the rock s on
-
-
,
,
,
98
MININ G GEOLOGY
.
The only evidence of the existence of su ch a fault is the
smooth pol i shed and slicken —sided s u rfaces on the line of move
,
,
FI G
.
56 — S
.
e tio n
c
sh
o wi g S eam p rt ly re mo ed
o f F lt
a
n
v
au
on
Both S i des alo ng li e
n
.
ment I n t he case of a min e ral vein , the faul t ing may result in
t he product i on of a lay e r of friction breccia on the side on which
th e movement took plac e
.
.
FI G
.
—S ec tio n
57
.
o f Par llel T hr t P lane
a
us
.
Such a fault i s mer e ly a thrust plan e more often th e result oi
shear i ng thrust than v e rtical or tangential stress
—
F
l
A faul t which runs in the same general direction
D ip
a u ts
as th e dip of a b e d or ve i n is te rmed a d ip fa ult
The d i st i nction bewe e n s t rik e faults and dip faults is not always
A fault may pursue any cours e b e tween th e s tr ike
w ell marke d
and dip of a bed When i ts course is m i dway between th e d i p
and strik e of the b e d the fault may b e termed either a dip fault
or a str i ke faul t
D ip —faul t s produc e an app a r en t lat e ral displacement of th e bed
or v ei n wh i ch th ey cross
Wh e n faul t ing tak es place th e pr i ncipal movement is a vertical
on e Consequently wh e n the faulted v ei n is vertical there is no
la te ral displac e ment or heave as the diss e vered e nds merely slide
upon e ach other
E v i denc e s of lateral thrust and shear i ng ar e often obs e rved
among Pal aeozoic sch i sts and gneiss but ar e sometimes seen in fault
-
‘
,
.
.
-
,
.
-
-
.
.
-
,
-
.
,
.
,
,
.
,
.
,
MININ G GEOLOG Y
1 00
.
displacement or downthrow ; and the cross c u t a o the amou nt of
lateral d i splaceme n t or h e ave
When th e drive da in fig 5 8 reached the fault the vein was
lost The lost vein was found at point c by cross cutting toward s
the east ; but obviously the pa rt of the vein struck at c was not
th e part corresponding to that driven on along da ( fig
I n this example th e fault dips t o the north 5 t her e for e the
Henc e the crosscu t
d ownthrow i s on the north sid e of t he fault
w i ll strik e a higher part of the v e in than that driven upon along ( ta
The downthrow is the distanc e a b and at I) will be foun d th e
conti nuation of the portion of th e vein driven on at a
S ometimes two or mor e faults run parallel with each other or
cross each other at an angl e I n other cases it happens that one
group of faults is int e rs e c t ed by another group of a later dat e
When faulted veins or s e ams are again faulted many complicat e d
problems becom e involv e d i n the recov e ry of the lost portions
S te p F a u lts — A s e am or bed is sometimes cross e d by a
number of faul ts runn i ng more or less parallel to e ach oth e r and
-
.
,
,
.
.
.
,
,
,
.
.
,
.
,
,
.
.
,
.
.
,
FI G
.
59
.
,
—
Cro ss
-
e tion
s c
sh
owi g G ro u p o f S tep Fault
n
s
.
d i pping in the same direction 5 or by some d i pping one way and
some another
S uch faults are often small and their e ffects best seen wh e n
they dislocat e a seam of c oal
.
,
.
FI G
.
6 0 — C ro s s
.
e tio n o f T ro gh Fault in D dley Port Mine
( ) S am o f c oal
( b) B l t
s c
-
u
a
e
u
.
a sa
.
S ta fl ords h ire
'
,
.
T HE
DYN A MI C S
AND
or L O D ES
B
E DS
101
.
Wh e n two pa rall e l faul t s d ip towa rds ea ch
o t her p e rmit t ing a po rt ion of s t rata to b e t hrown down betw ee n
them they form what is spok e n of as a trou g h fa ul t A w e ll
known example is the t rough faul t of D udl e y Po rt Mi ne in
S ta fi o rds h ire which has t hrown down the gr eat 10 ya rd seam a
distance of 4 5 0 feet as shown below
ro u g
T
h F a u l ts
—
.
,
-
.
,
-
,
'
-
,
,
.
R EC O VER Y . 0 F L
L
o sr
O
D ES
.
L o de s —
F our c a ses may occur when
driving on a vein dislocated by a faul t The v e in may dip to th e
right or l e ft hand and the faul t towards you or away from you
R u le s fo r I
n c lin e d
.
.
.
,
When the vein dips to th e l e ft and is cut o ff by a fault
dipping to wa rds you th e lost vein will be found by dr iv
ing to the l e ft
11 Wh e n th e vein dips to t he left and is cut o ff by a fault
dipping away from you t h e lost vein w i ll be foun d by driv
ing to the right
111 When the vein dips to th e right and is cu t o ff by a faul t
dipping towards you th e lost v e in w ill b e found by driv
ing to the right
IV When th e vein dips to t h e right and is cut o ff by a faul t
dipping away from you th e lo s t v e in will be found by driv
i ng to t he l e f t
Th e faul t may cross th e fac e of th e d riv e s quare ly or it may
cross obliqu e ly Th e angl e a t which th e fault inte rs e cts th e v ei n
do e s not affe c t t h e application of th e rul e s
V 1Vhen a horizon tal s e am i s cut o ff by a fault d i pping toward s
you its con t inua t ion w i ll be found a t a h i gh e r l e vel 5 bu t
wh e n t h e fault dips away from you th e los t sea m w ill
be found und e rfoo t
1
,
.
,
.
.
,
,
.
.
,
.
,
.
,
.
,
.
.
.
,
,
.
Thes e rules are alway s t ru e e xcep t in t he cas e of revers e d
faults and strike faults which run parall e l with th e s t rik e of th e
v ei n or s e am
—
Zimm e rman s graphic
Z imm e rm a n s G ra p h ic M e th od
me t hod for fin din g t he lost or faul t ed po rt ion of a lod e is as
follows
,
-
.
’
’
.
1
.
r ike of the lod e and faul t
down
upon
paper
t
he
l
i
n
e
of
st
y
producing t he l i n e s ti ll t hey in te rs e c t
D ete rmine by cons t ruction t h e poin t of inte rsection a t any
imaginary lower l e vel
D raw a line j oining t h e po in ts of inters e ct i on of th e lode and
fault a t the two levels
L
a
,
.
2
.
.
3
.
.
10 2
MININ G GEOLOGY
.
P roduce the lin e of i nt e rsection through th e fault at upper
l e vel
5 D ra w a line pe rpendicular to the fault at the point wh e re
the lin e of i nt e rsection e merges from th e faul t
R u le — O n what e ver side of the lin e of int e rse c tion produced
the perpendicular falls 0 11 that side will the lost l ode b e found
Z i mmerman s law is always tru e ex c ept in the c as e of r e versed
faults and strike faults
Unl e ss beds c a n b e recognised on each side of the fault the
e xtent of the throw cannot be dete r mined
A p p lica tion of R u le
E xa mp le 1 —
S uppose t h at in driving
north on a lod e a fault is met wi th which displaces the lode The
fault dips south at an angl e of
and the lod e dips w e st at
an angl e of
I n which dire c tion should th e lost portions
of the lode be found ?
4
.
.
.
.
.
,
.
’
,
-
.
,
.
.
.
.
V
FI G
.
61
—S ketc h
.
Pl n to i llu tr te Example 1
a
a
s
.
Procure a she e t of pap e r and plot t he approximat e position of
t h e lode and fault showing th e direction of dip of e ach with an arrow
L et the lode a n d fault be sho wn by a fi rm black l i ne as shown
in fi g 6 1
Plot th e position the lod e and fault would occupy at a low e r
depth say at 10 0 f e e t representing them by a t hin l i n e Produc e
t he lin e s till they meet T h e approxima te positions a t a lo we r
l e vel can be plotted by inspection for i t is ev i dent that if the lod e
dipping at 6 0 deg travels out say i ih ch in 1 0 0 feet th e lode
dipping at the fl a tte r angle of 4 5 deg will d i p much faster and
hence travel r e lativ e ly further out
The exact d e parture or dis tance the lode and fault will trav e l
out i n 100 feet can be found by mult i plying the cotangent of the
angl e of dip by 10 0
;
D raw a l i ne through t he points of inte rsection and erect a per
.
,
,
,
.
.
,
,
.
,
.
,
.
,
,
,
.
.
.
,
1 04
MININ G GEOLOGY
.
north instead of south at the sam e angle the diagram would be
as shown below
E xa mp le 5 — S uppose in d r iving no rth west on a lode dipping
,
,
.
-
.
FI G 6 4 —T o i llustrate Example
.
.
4
FIG
.
6 5 — T o ll us
.
i
tr te Ex
a
pe
m l 5
a
.
south west at an angle of
a fault were met with
E and W and dipping no rth at an angle of
on which
would the lost lode be found ?
-
.
.
,
FI G
.
66
i
T o ll us
.
trate Ex mple 6
a
.
Suppos e in driving east on a lode dipping sou t h
at an angle of
a fault were met with running N E
and dipp i ng S E at an angle of
wh e r e should the los t
portion of the lode be found ?
6
.
.
.
.
C H A FT E R V
.
O R E D E P O S I T S G E N E T I C A L LY C O N S I D E R E D
.
C ON T EN T S — Genetic Cl ific ti
C h ro mite i
Mag m ti c S egregatio
Peri dotite N i kel I o —N tive Copper P lati num M t l
Ore
di g
S o l fat ri — A tion o f A
fo rm ed b y Er pti ve A fter actio n
A lkal i e Water — Fumaro l i — Conta t Metamorph i c Depos it — Region l
M eta m orp h i D e po its — M eteo ri c W ter — O rg ni
'
as s
l
c
n
c
e a s
a
c
a
s
c
s
n
n
a
-
u
n
on
a
sc e n
c
a
s
a
c
n
a
s
c
s
s
.
Th e y ar e
O R E D EP O S I T S are of dive rse form and composition
foun d as tru e veins , as d e tached mass e s , and as members of a
sedim e nta ry forma t ion I t is now known that t h e ir mod e of
-
.
.
occurr e nc e and to som e e xtent th e ir compos i t ion and form w e r e
d etermined by th e g e ological conditions prevail i ng at the ti me of
the i r form at i on
I n t h e pas t decade a vast ma s s of fac ts has b e en add e d to th e
li te ratur e of the subj e ct par t icularly i n Am e rica wh e r e th e
magnitud e of th e op e rations conn e c te d wi th m i ning h as a ff orde d
gr ea t facil i ti e s for obs e rva t ion and res e arch
Th e gen e s is of or e d e pos its pr e s e nts many diffi c u l t probl e ms
and natur ally th e li teratur e of the subj e ct i s rich in t h e or e t i cal
d e duc t ions
Th e i n t roduction of pet rographica l m ethods of investigation
and th e d e mons t rat i on of th e princ i pl e s of metasomatic r e plac e
men t and s e condary e nr ichm e n t hav e mark e d a n e w po i n t of
d e pa rt ure and le d to a t ru e r conc e ption of th e forma t ion of or e
d e pos its than form e rly exi s t ed
I n this investigation w e m u st r e m e mb e r tha t e xis ti ng condi ti ons
ar e bu t a r e fl e c tion of th e pas t Th e ag e nci e s tha t bu i l t up t h e
crust of th e ea r th in i t s pr e s e nt form ar e still in op e ra t ion a n d
s ti ll govern e d by the sam e na t ural laws
We ar e l i ving on th e e dge of a geolog i c e poch and i f w e woul d
righ t ly und e rs tand t h e pas t we mus t s t u dy t h e pr e s e n t Th e
occurr e nc e of or e d e p os its i s m e rely a g e ologic happ e ning an
inciden t in th e te c tonic arrangement of t he materials form i ng the
out e r sh e ll of t he globe
—
Rec e n t petrogr aphi c al inv e stiga t ion has shown that ore d e posi ts
,
,
,
,
.
,
,
,
.
,
.
,
,
,
.
.
,
.
,
.
,
.
10 5
1 06
MININ G GEOLOG Y
.
are always mo re or less intimately connected with ign eous rocks
This c onstant association naturally l e ads to th e broad g e n e ra lisa
tion— T h a t ore dep osits G 7 6 g enetica lly connected with th e ei up tton
of i neous m a mas
g
g
.
-
.
G e ne tic C las s ifi ca tio n
.
The genetic c la s s ific a t ion which seems to most near ly sa tisfy our
present knowledge relati n g to mineral deposits is as follows
M agmati c segregation
II E ruptive afte r actio n s
1
.
.
-
.
l
a
t
ar
S
o
i
c
f
( )
b
F
u ma r olic
( )
t
n
a
t
m
e
a
ht
c
m
c
0
o
t
m
C
p
( )
d
eg ion a l m e ta morp h ic
R
( )
a
.
.
'
.
.
III M eteori c waters
.
l
h
m
i
a
e
C
c
( )
6
ech a n ica l
M
( )
a
IV
O rga n ic
.
.
.
.
I
M A G M AT I C
—
.
S E G RE G A T I ON
I t has b e en shown by Professor
.
and others
igneous rocks c ontain all the co n stituents of min e ral veins
Professor Vogt of Christiania maintains that a deep s e ated
ina c c e ssible re pository of the heavy metal s can no longer b e
1
sustained
M odern geologists h e points out hav e abandon e d
t h e old conception of the earth s inter i or condition which su pposed
that the int e rior was an enormously compress e d liquid molten
mass of high s p e c ifi c gravity charg e d with heavy m e ta ls
The compos i tion of the molten magmas that hav e issu e d at th e
s u rface in suc c essive geologi c al ages do
th e sis which assumes th e e xis t ence of a
h e avy metals in the barysphere than in the upp e r crust or litho
sphere
R e ferring to the distribution of the e l e ments in the e arth s
crust V ogt states that of th e entir e crust i ncluding
and atmosphere oxygen cons t i t utes by weight about
2
silicon above one quarter
S a n db e rg e r
,
.
-
,
,
,
.
,
’
f
,
.
,
.
’
,
,
,
-
.
1
G
Pro fe or
in th e
ss
f
en es is o Or e D ep os tt3
,
2
L oc. c it , p . 6 39.
1 90 1 , p 6 37
.
.
O rigi n o f
Ore
Depo s its
”
,
1 08
GEOLOGY
MI N I N G
.
resulting from direct di ff erentiation in th e cooling magma are
follows
,
rpentine
Ch
omite
in
peridotit
e
and
se
r
( )
Copper and nickel iron in serp e ntine
0 ) Platinum m e tals in highly basic eruptives
(
M
agnetite
and
titanite
in
basi
and
semi
basic
eruptives
d
c
( )
a
as
.
-
.
.
-
.
the South I sland of Ne w
Zealand there are two mo u ntain masses of p e ridotite in which
th e magmatic segrega t ion of c h romit e is exhibited on a large
s c ale
A few m iles from the city of N elson D u n M ountain rises to a
h e ight of over 40 0 0 feet abov e sea l e vel I t cove rs an area of
about 4 square mil e s and is compose d of massive olivine in wh i ch
chromit e of iron is uniformly disseminated in the form of fi n e
1
grains but occasionally occurs in large masses
Th e adj ac e nt ro c ks ar e slaty shales and limestones of probably
J u ra ss ic ag e th e limestone occurring at the base of sedimenta ry
formation B e tween the lim e stone and the olivine to which
2
Ho c hstetter gav e th e distinctive nam e dunite there is a belt of
s e rpentin e half a mile wide
The serpentin e contains l e nticular shaped masses of chromit e
native copp e r and copper ores principally chalcopyrite with th e
usual prod u cts of oxidation I t also contains thin irr e gular v e ins
of diallage bronzite enstatite scapolit e wollastonite and chryso
tile
T h e larg e r masses of chromit e in the olivine and serp e ntin e
o c cur along t he ma rgin or boundary of t hese rocks
Th e s e cond g rea t mass of peridotite forms R e d M ountain
3
situated 2 0 miles north of M ilford S ound in O tago
I t is over
6 0 0 0 feet high and covers an area of about 1 0 square miles
The mountain is composed of olivine and chromite Th e latter
occurs in much greater proportion t han at D u n M ountain
Th e p e ridotit e is flanked on two sid e s by bel t s of s e rp e n t in e
which separate it from the adj a c ent slat e s and sandstones of
suppos e d Pal aeozoic age
The olivin e n e ar th e con tact with the sedimentary rocks 1s
often so highly charged with chromit e as to form massiv e bodies
of ore N o d e posits of c hromite are known in the se rpentine but
C h ro m ite in P
e rido tit e
-
.
I
n
,
,
.
,
-
.
,
,
,
.
,
,
.
,
.
-
,
,
,
,
.
,
,
,
,
,
.
.
,
.
,
,
.
.
.
,
.
,
,
.
,
Co
C o e
epo it o
e o
”
S H
hr m D
x,
f N l s n, N ew Z ea la nd G eol R ep or ts
s s
a nd E xp lor a tions , 1 88 1
8
, p
2
Dr F Von H O Ch S te tte r’ 2 5 1 3 0717 173 de f deu ts che n ge ol G esells , xv p 34 1 ,
1 864
3
J
ar , N e w Z ea la nd G eolo ica l R e or ts a nd E x lor a tions ,
87,
1886
g
p
p
1
.
.
“
.
.
.
0
'
.
.
P k
.
.
i
.
.
D E P O S IT S
ORE
N ET I C ALLY C O NS I D E R E D
G E
1 09
.
they may poss i bly exist as th e count ry is still p ra cti ca lly
,
un
—
I ro n
The sands in the s t reams which dr ain th e R e d
M ountain se rpen t in e area yield small quant i t i es of th e rare nick e l
i ron alloy Awaruite d iscover e d by W Sk e y i n
I t has
be e n found in situ i n t he s erp e nt i ne
A ni ck e l i ron alloy th e sa m e as or r e lated to Awarui t e h as b ee n
found i n gold bea ri ng sands a t t h e Riv e r B ie lla P i ed mon t
3
i n s e rp e n
ass oc i a t ed with chrom it e se para ted from per i do t ite ;
4
ti n e i n J os e ph in e County O r e gon ; in sands to ne ass oc i a te d wi t h
5
chromi te i n Fras e r R i v e r British Col u mb i a ; and i n Smi t h
R i ver D e l N o r te County Cal i fornia
—
The associa ti on of co pper and chromite in
N a tiv e C o p p e r
the serpen t ines a t D u n M oun ta in has alread y b e en m e n ti on e d
N a t iv e copper is foun d in s e rpent ine in Cornwall Ne w Sou th
“tales a n d ma ny oth e r pa rt s of t he world
Larg e mass e s of na ti v e copper assoc i ated wi t h silver are found
in amygdalo i dal d i aba s e a t L ak e S u perior
I n 18 7 9 Prof S H Cox di s cover e d in th e M anukau d is trict a
number of dyk e s of and e s it e which near the i r bo rders wer e
foun d to con tain small gra i ns of na t ive copper fi n e ly d i ss e m i na te d
6
throughou t the i gneous ma t rix
The dyk e s ar e i n t ruded in
volcan i c br e cc i as of probably la ter Mi oc e n e ag e
P l a tinu m M e tal s — Pla t inum has only b ee n found i n a f e w
cas e s i n t h e ma t rix in mtu a n d i n most case s i n basic or ul t ra
bas i c rocks
I n the Ural M oun ta i ns i t occurs as gra i ns in
p e r i do tite and s e rpentin e
The b e d rock of t h e Vy za j and Ka iv a rivers on t h e western
fl a n ks of t h e Ural s cons i sts of olivin e gabbro con ta i n i n g d i s
s e m i na t ed g rains of pla t inum but not apparently in pa yabl e
quant itie s
A n ol i v i ne rock was d iscovered in 1 8 93 at G or ob la g e —
da ts k
on t he wes te rn s i de of th e Urals conta i n i ng ch romite a n d
p la ti num t he la tter at th e rate of 1 4 d wt 9 g r to t he to n of rock
7
Carm i chael in 1 90 2 repo rt e d the occur renc e of plat i num i n a
fi n e—gra i ned dark basal ti c rock
N ic k e l
.
,
.
,
,
.
,
-
,
,
-
,
,
,
,
,
,
.
,
,
.
.
,
,
.
,
,
.
.
,
.
,
,
.
,
,
,
,
.
.
.
’
,
.
,
.
-
,
-
,
,
,
.
,
,
,
“
.
,
.
.
,
,
.
W
key
iii
40 1 , 1 885
T r a n s N Z I ns t , v ol x x
, p
9
G H U lr c h ,
f cc urre nc , a n d D s r u i n
O u t h e D sc v ry , M od
s
f th e N ic keI - r n ll y waru on th e
as f th e S u h I sla n d f
”
N e w Z a la nd , Qu a r t J ou r G eo S oc
L nd n
3
Comp te s R on d us , c x
p 171
4
A m J ou rn S e
xi x p 3 19, 1 90 5
5
L oc cit , p 31 9
6
S H
x, G l gy f a Ro dn y , N Z G eol Rep orts a nd E xp lor a
timw, 1 8 79 80 , p 2 7
7
E n g a nd M in J o an , N e w Y r , Fe b 1 2 , 1 90 2
1
S
.
.
o
.
e
,
.
.
i
i o e
io A o A
ite
.
.
.
.
.
.
.
Co
.
.
.
.
.
.
.
.
.
ii
.
.
eo o
.
.
.
.
eo O
e
We t Co t o
o o
.
.
.
.
o C pe
e
.
.
.
-
.
.
.
.
ok
.
.
i t ib t o
o t
o
1 10
GEOLOG Y
MI N I N G
.
Pond in 18 86 discovered native platinum in serpen tine at
Wade n ear Auckland and in a great vein traversing propylitised
and e site at the Tham e s g oldfi e ld
S i nce the discov e ry of platinum in the nickel c opper sulphid e
ore at Sudbury in Canada careful analysis has d i s c los e d th e
presence of the metal in minut e quantity in many sulphide ores
t hroughout the world But in this and all cases where platin u
occurs in sulphid e b e ds or in veins its oc c urren c e is probably not
th e result of d i rect magmati c segregation
I
A
.
,
,
.
,
,
.
-
,
,
.
,
,
,
.
II
.
O R E s F O R M ED
E R U P T I VE
B Y
AF T ER A C T I O N S
-
.
I t is manife st tha t the whole series of e r uptive after actions w ill
-
commence at th e movement of intrusion of the magma and c on
tin u e until the rocks hav e become compl e tely c ooled
I gneous magmas are now admitte d by petrologists to contain
mor e or less water toge ther with many constituents of a hydrous
or gaseous charact e r
Hence th e fusion of magmas is not believed to be pyrogenet i c
that is th e result of dry hea t alone but h yda to pyrogenet i c t hat
i s fusion by heat in the presence of water According to
1
Arrhenius water renders the magma more l i quid
I t has b e en shown by e xperiment that magmas which require a
te mpera t ure of 3000 F t o prod uce dry fusion can be fused
i n th e presence of water at 5 00 F
F urther it has b ee n
shown that the pr e s e nce of water aids in giving a magma fl u idity
2
Barus was abl e to fuse glass at 2 00 C in the presen c e of water
According t o Arrh e n i us water i n a mag m a a c t s the pa rt of an
ac i d l i bera t ing free s i licic acid a n d free bases
The a c tivity of wat e r at high t emperature is very gr e at
3
Barns has shown that wa t er heated above 18 5 deg C a t tacks
th e silicates compos i ng soft glass with remarkable rapid i ty and
L e mberg has proved experim e n t ally that water at a temperature
of 2 10 C slowly dissolves anhydrous powdered silicates
I t is probable that at gr e at depths the pressure will be
s u ffi c ie n t to hold the water in the form of a liquid in a sup e r
4
h e at e d condition
A t high temp e ratures both wa te r and steam
possess a great capaci ty for d i ssol ving min e ral substanc e s
,
.
.
,
-
,
,
,
,
,
.
.
,
"
.
,
°
,
.
°
.
,
.
,
,
.
,
.
,
.
,
,
.
,
,
°
.
,
.
,
,
,
,
.
.
te A
e i
P
ik
k i
or
rrh n u s ,
S v an
Z ur
hy s
de s V u l a n sm u s , G eol F or e n F k
S tockh ol m , 1 90 0
2
C B aru s , A m J ou
S ci , i p 2 70 , 1 8 98
”
3
a rn s ,
a
r a n d S f G lass in h r T h rm dy n am c Re la n s
C
S ci I V , v ol i , 1 90 0 , p 1 6 1
A m J u
4
s ,
S m
r nc l s c n r ll n th e D s n f r s ,
O R Van
T r a n s A merica n I ns tztu te of M i ning E ng in eer s , v ol
2
7
p
1
“
.
.
.
.
.
B
o r
.
.
.
.
r
Hot W te
.
.
v
.
.
.
.
Hi e
x
.
.
ot
.
.
t ei
.
o e P i ip e
e o
.
o to i g
’
.
.
xxx
i
tio
epo itio o O e
.
.
.
.
1 12
MININ G GEOLOGY
.
Where the hot springs ov e rfl ow on the surface they form
thick mushroom shaped mounds of silica The silica is some
times soft and porous and often de n se hard and chalc e donic
I n all c ases the hot springs and geys e rs are grouped around
th e volcanic vents and along fi s s u r e s in lavas n e ar th e point of
e miss i on
—
I n th e Hauraki gold mining area which a dj oins th e north e rn
e nd of this volcanic region t he country rocks consist of a vas t
p i l e of and e sitic lavas tu fi s and br e ccias of M ioc e ne ag e resting
on slaty shales and greywack e of probably Tr i ass i c age
Th e gold bearing v e ins traverse both the and e s i t e s and t u fi s
but are only pro ductive in th e former They are fis s u re v ei ns
but strictly speaking th e y do not conform to the usually acc e pt e d
d e fi nit i on of a t rue fi ss u r e v e i n since th e y are g e ne rally c on fi n e d
t o th e igneous rock formation
Ne ar the bord e rs of th e and esites the veins are small and u n
important and g e nerally die out when they reach the underly i ng
basement rock On t h e other hand th e larger and more pro
du c t iv e veins are group e d around the old vents and have been
found to descend as deep as m i ning operat i ons have followed them
Ther e seems to be no reason why t h e y should not des c end to
great depths
Th e country rock on the walls of t he veins is propylitised to a
moderat e ly hard gray rock When two or more v ei ns run parall e l
with each other as th e y do in all th e Hauraki mini n g centr e s
the country rock between the v ei ns is often entir e ly altered or
propylitise d
I n the Tham e s district the distance b e tween the numerous
parallel veins which traverse the g oldfi e ld seldom exc e eds 2 00
yards and in almost every instan c e th e veins are s e parat ed from
each other by a narrow belt of hard unaltered andesite These
hard bands or ba rs as the mine rs term them possess the sam e
general strike and dip as the veins and in cross sect i on pres e nt
t h e appearanc e of l e nticular and hourglass shap e d masses They
vary from a f e w feet to 30 yards in width
The country rock has b e en found to be propylitised down to a
d e pth of nearly 10 0 0 feet below sea l e v e l wh i ch is th e greatest
depth reach e d by mining op e rations up to th e pr e s e nt time
The propylitisation of t he andesites is not wid e spread but
c on fi n e d t o small areas grouped around th e old volcanic vents
Away from the eruptiv e c entres th e andesites have su ff e red
surfac e decomposition but are not propyl i tised
The propylit i sa t ion was apparently e ff ected by hot mineral
waters circulating in fissures wh i ch are now fill e d wi t h ve i n
matter F rom these fi ssu re s the mi n eralised w aters a c ted on the
,
-
.
,
,
,
.
,
,
.
,
-
,
'
,
,
,
.
’
-
,
-
.
,
,
-
,
-
.
,
,
,
.
,
.
.
-
,
,
.
,
,
-
,
.
,
,
.
,
,
-
,
-
.
.
-
-
,
.
,
.
,
,
.
.
O RE
D EP O S I T S
G E
N ET I C ALLY C O N S I D E R E D
1 13
.
rock on e ach wall ; and where the fi ss u r e s wer e near eac h o t her
th e m etasoma ti c ag e nc i es opera ti ng from one fi ss u r e m et t hos e
coming from th e o t h e r Wh e re the proc e ss e s of al te ra ti on did
not m eet narro w irregular sh e e t—l ik e mass e s of unal ter e d rock
th e bars of the m i n e rs — w e r e left b e twe e n the v e in fis su r es
A t Waih i a n d surroun di ng d i s t ri cts t he veins are pr i ncipally
compos ed of chalc e don i c quart z possess ing all the chara c t e ri s ti cs
of solfat ari c or i g i n S om e of th e larg e r lod e s can be t raced on
t h e surfac e for a d i s t ance of
f e et but th e l e ngth of the
majority i s und e r 5 0 0 0 fe e t
Be s i des the v e in s having l i n ea r e xtens i on th e r e are many hug e
mush r oom—shap e d mass e s of chalced onic quar t z clos e ly r e s e mbl i ng
in form t h e s i l i c eous deposits now forming in th e volca n i c r e g i ons
around Rotorua and L ak e Taupo
A t Kuao t unu and G reat Ba rr ie r I sland t her e ar e many of these
mushroom shaped deposi t s in some cas e s covering hundreds i n
o th e rs t housands of acr e s A t Kuaotunu t hey ar e more or l e s s
circular in s hape and s e ldom e xc e ed 2 0 f e e t i n thickness
A t G reat Barri e r I slan d the larg e st d e pos i t is of an unusual
1
charac ter
It i s nearly 2 m i les long h alf a mile wid e a n d
from 5 0 to 7 00 fe e t thick
The pip e i s c omple t ely fille d wi t h mineral matte r I t has b e en
i ntersected i n fo u r m i nes in a distan c e of a mil e and opened up
by lev e ls for many hundreds of ya rds It varies from 1 2 to 4 0
f ee t i n w i d th and i s filled wi t h v e ry de n s e banded chalced on i c
qua rtz in wh i ch i ron and s i lver sulphides are s pa r i ngly d i s
tribute d
The evidence furnished by t he mine workings implies t hat t he
overlying mushroom or umbr e lla of quartz was depos i ted on th e
surfac e from th e r mal wat e rs i s s u in g from a fi ss u r e i n t h e an de s it e
Th e molybd e nit e depos its at Jeff s Camp in t h e Hodgki nson
2
l
o
fi
ld
W
in
Qu
ee
nsland
ar
e
d
e
scr
i
ed
by
E
Cameron
as
d
e
b
g
roughly c i rcular or oval shape d outc rops of quartz or blows
carrying wolfram and na t iv e bis muth
The blows wh e n follow e d down d e velop into i rr e gul ar p i p e
shap e d masses surroun ded on a ll sides by gran i te wh i ch is t h e
co u ntry rock Wh e n t he quartz i s extracted there remain only
e mpty pipe s or vents
These p i p e l i k e or e bodies poss ess a pecul i ar in te rest from a
g e ne t ic s tand po i n t Th e y appear to closely r e s e mbl e t he s i l i c e ous
p i pes formed i n rhyolite by th e hot springs in t he Rotorua
,
,
,
.
,
,
,
-
,
.
,
,
.
,
.
,
,
.
-
,
,
,
.
.
,
,
.
,
,
.
.
,
,
.
,
,
.
.
’
,
,
,
,
.
.
-
,
,
,
.
,
,
,
,
-
,
.
.
-
-
.
1
N
.
Z
2
J
.
.
I
P rk
a
,
Q
ue e
T he
G eol ogy
an d
v
Veins o f H au raki
G
o ld fie lds ,
M i n ing E n g ine er s , ol i p 1 37, 1 8 97
“
E C am r n
l fram a n d M ly d n e M n
ns la n d G eo ] S u r v ey R ep or t, N o 1 88 , p 7 , B ris an
n s titu te
W
al te r
”
l and,
“
eo
.
,
Wo
.
.
.
.
o b e it
f
.
.
.
”
T r a ns
i i g i Q ee
b e 1 90 4
n
n
u
.
,
8
.
ns
.
114
MININ G GEOLOGY
.
volcanic region and the mushroom shap e d quartz blows at
Kuaotunu
S everal of the massive d e posits of chalc e donic qua rtz a t Waihi
are stated by F rank Rutl e y to be r e placements of the an desi t e
1
c ountry ro c k
A similar r e placement of andesite by silica is d e scr i b e d by
2
Spurr as oc c urring at M onte Cri s to district i n Wash i ngton
He mentions that t h e s ilic ifica t ion has proce e ded un t i l most of t h e
rock is made up of quartz wh i ch he says varies from coarsely to
very fi n e ly crystalline in structure and conta i ns sulphides c h ie fl y
blende pyrit e s ; and chalcopyrite in lenses of ore concentrat e d
along j oint p1anes bedd i ng planes and c on tacts
Spurr continues Thus we hav e a complete and gradual transi
tion from andesite to a sulphi d e ore with a quartz gangue by the
progressiv e r e pla c ement o f t h e original materials by s i lica a n d
”
metall i c sulph i des
I n 18 94 and 1 896 the author mad e an exhausti v e examination
of the Hauraki and e sit e s for gold and s i lver
The samples subj e c t e d to examination were s e lect e d in s itu
Th e analyses wer e conducted by th e cyanide test on s amples
ranging from two to fi v e pounds in weight The pulv e rised
material wa s l e ached w ith a 0 3 per cent aqueous solution of pure
potassium cyan i d e for seventy two hours
The cyan i d e solut i ons and washings w e r e e vapo rat e d fi u xe d
with pure lith a rge and the result i ng but t on of l e ad cupelled
S i multaneous tes t s w ere made on pure subs tan ces so as to check
the results
All the and e sit e s were found to contain gold at the rat e of 1 5 g r
per ton and silv e r varying from 3 g r to 30 g r p e r ton of rock
Th e aug i t e andesit e at 30 0 0 feet from th e mou t h of th e
M oa n a ta ia r i tunnel conta i ned 1 % g r of gold and 3 g r of silver to
th e ton and the hyp e rsthene aug i te and e s ite from th e wat e rfall
in Waio tahi Creek near the F ame and F ortun e mine contain e d
3
1 4 g r of gold and 30 g r of silver
A petrolog i cal examinat i on of the rocks showed that the felspars
4
were often kaolinised and the pyroxenes generally much alter ed
The samples were s e l e cted from the least altered rocks obtain ed
and in no c ase did th e y contain v i sible pyrites
-
-
,
.
-
.
,
,
.
,
,
,
,
,
-
.
,
,
,
,
,
.
,
.
,
,
.
,
.
.
-
.
,
,
.
,
.
.
.
,
.
.
-
,
,
.
.
-
-
,
,
,
,
,
.
.
.
,
.
,
.
te
ote
o o lv
o ite o
H
ki
P a1k an d F R u l y ,
N
s o n Rh y l
f th e aura G oldfie lds ,
s
1 8 99
Qu a r t J ou r na l G eol S oc , L n d n ,
,
”
2
J E S u rr, U S G eol S u r v ey T we n ty S ec on d A n n u a l R ep or t, 1 90 0—1
”
s
s,
ar I I
O re D
p 833
“
”
3
ar ,
l y a n d V n s f au ra
T he G
T ran
G ol d fie lds ,
N ew
Z ea la nd I ns t M E , 1 897, p 5 2
“
1
nd s
S m
ar
J
s fr m th e T h a m s G ol d fie l ds ,
T r a n s N ew
Z ea la n d I n s ti tu te , v ol
i , p 4 35
1
J
.
.
.
P t
.
.
p
.
J P k
.
P k
.
,
.
.
.
.
.
eo og
.
o e A e ite
xxx v
.
.
.
.
epo it
.
.
.
‘
.
ei
o
o H
ki
e
.
s
.
.
11 6
MIN IN G GEOLOGY
.
charg e d to gal e na from th e V esuvian mine F r eihung in Bavaria
I n thes e th e fib r e a n d annular r i ngs coul d be eas i ly recogn i s ed
1
b ei ng extr e m e ly pla i n on polish ed surfaces
M r R B A u dr em on t (B u ll d e la S oc G é ol B e lg iqu e) stat e s that
in a pitchblende min e at Joachimsthal in Bohemia a pi e ce of
carbon i s e d wood from a dec i duous plant was found in a fi ssu re
fi ll e d with volcan i c tu ff at a d e pth of 915 f ee t
I n th e tu fts assoc i at e d with the Hauraki gold b e aring andes i tes
mass e s of wood partly or wholly s ilic ifie d and spangled with nests
and v e ins of iron pyr i tes are of common occurrence
T h e M artha lo d e and i ts num e rous ramify i ng branches a n d
th e S i lverton Union and Amaranth lod e s at Waih i are all con
Th e huge lod e s w i d e
t a in e d in an area of abo u t a square mile
zones of s il ic ifi e d and e sit e and ex te nsiv e propylit i sation of the
and e s i te prov e that Waih i was an area of int e nse hydrothermal
acti vity som e time prior to the eruption of the later rhyolit e
fl o ws which now form the plains and wrap around the M artha
and Silverton veins
The propylitisation has already been shown by the Waihi mine
workings to e xtend to a d e pth of nearly 8 0 0 feet below pr e sen t
water lev e l that is some 4 0 0 feet below sea l e vel O bviously th e
alteration of the and e site was due to the action of as c ending and
lat e rally moving thermal wa t e rs
A t Thames and Coromandel som e of the m ost productive v ei ns
do not reach th e surface of the e nclos i ng rock 5 and th e m i n e
workings at Waih i have d i sclosed a similar f e ature in conn e c ti on
2
with a few valuabl e v e ins in th e Waih i Company s property
I n 1 8 98 Captain F W Hutton
as the r e sult of a
petrographical examination of th e Tham e s mining district con
3
clud e d that the veins w e re of hydroth e rmal orig i n
T A R i ckard a well known American geologist who exam i n e d
the same g oldfi e ld in 1 891 wh en discuss i ng Professor P os e p ny s
”
pap e r on The G enesis of O r e D eposits describ e s t he character
is tic features of t he district with the view of adducing a dditional
ev i d e nce of the associat i on of thermal springs and la te r e ruptiv e
4
He states t hat his examination of the ore occurr e nc e s and
rocks
vein structure though incomplete led him to con clude that the
.
,
,
,
.
’
.
.
.
.
,
,
,
,
.
-
,
,
.
,
,
,
,
,
,
,
,
.
,
,
,
.
-
-
,
,
.
,
.
‘
’
.
,
.
,
.
,
.
-
.
,
,
.
’
,
,
,
-
.
-
,
Pro fe or Fra z P p y
P 0 M o rga
N ote
”
Waih i G ld fi ld T
1
n
ss
2
.
th e
viii
,
n,
.
o
.
p
F
.
1 68 , 1 90 2
W
os e
n
“
e
,
,
s on
r a ns.
T h e G en esis of Ore D ep os its , p 1 2 9, 1 90 1
R fs , a n d M n ral s f
th e G l y , Quar
A u str I n s titu te of M in ing En g in e ers , v ol
eo og
tz ee
.
i e
o
.
.
.
H tton
.
ok o
H
ki
o
eo
i
io
”
T 7 a n3
f th e au ra
G ol dfie l d ,
O u th e R c s
“
A u s t A ssoc A d v S o ,
vi p 2 4 5 , 1 888 ; a n d S u rc f G ld a th e
”
T h am s , N Z J ou r n a l of S c ience ,
1 p 146
4
A
T
R c a rd, T he G enes is of Or e Dep o s its — D s c u ss n , N e w Y r ,
1 90 1 , p 2 22
3
.
u
.
.
.
.
e
.
.
.
.
.
.
ik
,
vol
.
ii
.
.
vol
.
.
.
.
o
'
.
t
ok
oar.
D EP O S IT S
G E
N ET I C ALLY C O N S ID E RE D
1 17
.
d e posi t ion
of the gold and its associated minerals h a d followed
ce r tain lines of altered coun try rock which h ad be e n e xpos e d t o
th e e ffe c ts of dying but ling e ring s olfataric ag e nci e s
Th e O ha e awa i Hot Spri ngs quicks i lv e r de pos its nort h of t h e
Hauraki peni nsula ar e of gr e a t importa n c e on accoun t of t h e
evid e nce which t h ey furni sh in conn e ction wi th th e g e n es is of
solfa ta ric or e d e posi ts
The bas e m e nt rocks co nsist o f low e r M esozo ic shal e s and
T e rti ary or uppe r
s ands t ones ov e rlain by gr ee nsands of lo w e r
Cr e tac e ous age which are cov e red wi t h fl o ws of basal t and bed s
of scoriae It i s agr e ed by all geo log i s ts t ha t th e basal t cons t i t ut es
t h e young e st roc k forma ti on in t h e dis t ri c t
Th e surro u n din g coun t ry is studd e d wi t h old c rate rs ; and t h e r e
is e v e rywh e re e vidence of former i ntens e volcanic ac t ivi ty
Th e ho t springs aroun d which th e quicksilve r d e pos i ts ar e
cl u s tere d are situa t ed abou t two mil e s sou t h ea s t of La k e
O map e r e wh i ch i ts e lf occupi e s t h e site of an old cra te r
Th e y occur along the ed g e of a fl o w o f basalt wh i ch is ov e r
lain a t t his poin t by d e pos i ts of ca lcar e ous and sil i c e ous s i nte r
and so lidified sil i ceous and carbonaceous muds t h rough wh i ch
s ulphur and cinnabar ar e fi n e l
i
ss
e
mina
t
ed
d
y
There ar e a lso d e pos i ts of py rites w i t h or wi thou t c innabar in
1
som e cas e s conta in in g trace s of bo t h gold and s ilv e r
Th e
s in ters also contain gold and s ilv e r
The ground around t he springs is g e nerally very hot 5 and all
a t temp ts to d e v e lop the quicksil v e r deposits have b e en frus t rated
by t h e large volum e s of hot water e ncoun tered a t shallow d e pths
be low th e s u rfa c e
Th e d is t r i c t has been e xamined a t diffe r e n t t im e s by Cap ta i n
Hu tton Sir Jam e s H e ctor A M Ka y and t h e au thor ; bu t t h e
bes t d e s cri pt i on is that of Andr e P G riffi th s who con ducted
e x tens iv e pros pec ting a n d mining ope ra ti ons ther e i n 18 95 a n d
-
,
.
,
,
,
-
.
,
.
-
.
.
,
-
,
,
.
,
,
.
,
.
.
.
‘
,
,
,
.
.
18 98
,
.
The mining O pera t ions and bori n gs disclos ed many im po r ta n t
d e tails wh i ch could not be gathered from a surfac e e xamin a
,
The iron pyrite s occu rs in ma ss e s near th e basalt and also fill
ing c racks a n d fi ss u re s i n that roc k Th e thickn e ss of th e masse s
varies from 3 inch e s to 3 f ee t but their oth e r d i me ns ions ar e
extrem e ly irr e gul ar
Clos e to the pyri t ic mass e s th e re is a hard whi te s i l i c e ous
sinter from 8 to 1 0 i nch e s t hick w h i ch G r iffi ths fo u n d to
contain gold and s ilver in places O n e assay of th e sinter gave a
1
An dre P G riffi th s T h e O h ae a wai Qu ic k s il ver Depos its T r a ns N ew
,
.
,
.
,
,
,
.
“
.
Z
e a l a nd
I
n s tit u te
,
M in ing E ng
.
,
v ol
.
ii
,
.
4
p 8
.
.
.
11 8
MININ G GEOLOGY
.
valu e of £ 3 per ton but unfortunat e ly th e propor ti ons of th e
1
gold and silv e r are no t g i v e n
Th e cinnabar g e n e rally occurs l i ning small caviti e s and cracks
in th e s olidifi e d muds and sint e rs surround i ng the original fi ss u re s
in th e basalt I t also occurs impr e gnating the sinter in an e x
t r e m e ly fi n e ly divided form
S u lphur occurs throughout the sinter in larg e r propo rtion than
eith e r the cin n abar or pyrites
T h e hot springs give 0 11 large quantities of H 2 8 and occasion
ally a lit tl e steam Th e gas escaping through the wat e r of th e
pools and small streams is partially oxidised l i berating sulphur
which imparts a milky white colour to th e pools locally known
as whit e lakes
The b e a c hes of the so call e d whit e lak es co n sist of sulphur
mixed with magn e tic ir on sa n d and a small proportion of alum
Sulphur is also b e ing sublim e d at th e vents or openings in th e
rocks from which 11 2 8 and S O 2 gases e scape
T h e prospecting work conducted by G r iffi th s disclosed som e
inter e st i ng features
A d e posit of cinnabar and pyrites crops out a t the foot of th e
hills to the south w e st of the main deposits A shaft was sunk
n e ar it and cut the lode at a depth of 35 f ee t The or e was 2
f e et thick and consisted of small crystals of pyrites cem e nted by
cinnabar A t th i s d e pth t here was a strong evolution of HZ S
a n d th e h e at of the rocks increased so rapidly with the d e pth
that mining was extremely diffi c u lt
I t is noteworthy as showing th e r e c e n t formation of th e cin
nabar that n e ar the outcrop of this lod e was found th e charr e d
t runk of a tr ee part i ally emb e dd e d in hard siliceous mud Th e
trunk and roots of th e tre e were coat e d with a t h i n fi lm of c i n
nabar as also w e re some pi e ces of fossil kauri gum found near
the roots
I n a small trench sunk over a fumarol e t h e temperatur e of th e
rock at a d e pth of 10 feet was found to be 1 8 5 F ahr
N o 1 bor e hole cas e d with 3 inch piping was put down to a
d e pth of 10 4 fe e t wher e it e ncountered th e e dg e of th e basal t
A t th e same t i me it struck a fi ss u r e from which hot mud was
proj e ct e d a h e ight of 60 fe e t abov e the s u rfac e for about forty
e ight hou rs
The mud was succeed e d by boiling water charg e d with H28
gas w hich was found to issue at a pressure of 30 1b p e r square
inch
G r iffith s further ment i ons that th e richest deposits of cinnabar
were found in clos e proximity to th e hottest fumarol e s and that
1
A ndre P G riffi th s loo cit p 5 0
,
.
.
.
.
,
.
,
,
.
-
,
,
.
,
,
.
.
-
,
.
,
.
,
,
.
.
,
,
,
.
,
.
,
°
.
-
-
,
.
,
.
,
,
.
,
,
.
.
,
.
,
.
.
,
.
.
120
MININ G GEOLOG Y
.
Baron von Richthofen who examined th e Comsto ck lode at
a time wh e n no abnormal te mperatu re was noticeabl e ascrib e d th e
origin of t h e lod e to e arl ie r solfa taric action
Th e quicksilv e r mines at Sulphur Bank in Californ i a furnish
—
impor tant e videnc e in r e lation to the gen e sis of or e d e po s i ts
A t this plac e the basement rocks are slate and san dstones
ov e rla i n by a freshwater form ation which in turn is capp e d by
a fl o w of basalt The geologic f e atur e s ar e almost id e n t ical with
thos e existing a t O haeawai
Th e sandstones and slates are broken and fi s s u re d in such a
way as to form a br e ccia
Th e int e rspac e s ar e fille d partly wi t h
a still sof t or alr e ady indurat e d siliceous past e containing fin e ly
diss e minat e d metallic sulph i d e s and partly wi th cinnabar for th e
2
most part in coh e r e nt crusts
I n th e sam e min e th e basalt i s reduc e d to a porous m ass
and trav e rs e d by irregular fi s s u re s fi lle d wi th sulphur and
3
cinnabar
Hot m i neral wat e r and gas e s carrying H2 S forc e their way
through th e int e rstic e s of t h e d e po sit i n the fi s s u r e d sandston e s
and slat e s
The silica deposits are found in all stages of consolidation from
a g e latinous mass to chalcedony and alt e rnat e with layers of
m e tall i c sulphid e s consis t ing of cinnabar and pyrites
Unfor tuna t ely no i nformation is ob tainable as to th e nature of
th e fr e shwat e r formation lying b e tw e en the Cr e taceous sa nds ton e
and basalt
According to B e cker the hot water is rich in c hlo r ides borax
and sodium carbonat e The gas e s l i be rat e d from th e wat e r con
sist e d of 8 93 parts of 0 0 2 2 parts of HZ S 7 9 parts of marsh gas
and 2 5 parts of ni t rogen in 10 0 0 parts
Accord i ng t o D r Me lvill e th e marcasit e associated with th e
cinnabar contain e d traces of gold and copper and in th e
e filor e s c e n c e from the m i n e workings
Becker detected trac e s of
cobalt a n d nick e l
I n t he upper zone only sulphur was found low e r down sulphur
and c i nnabar and in depth c i nnabar and pyrit e s occurring upon
or within d e posits of silica
The St e amboat Springs in N evada furnish equ ally important
1
,
,
,
.
,
,
.
,
,
.
.
.
,
,
,
.
,
,
.
,
,
.
,
,
,
.
.
,
,
,
.
,
,
.
,
,
,
‘
,
.
,
.
,
1
F
i h th o fe
,
T h e Com stock L ode I ts Cha r a cte r a nd P r oba ble M ode
of Contin u a nc e in D ep th , S a n F ranc sc
1 86 6, p 5 4
,
2
L e
n
O u M n ral V n s n ow in r r ss a S am a S r n s
,
”
c m ar d w h th e s a m
a S ul h ur B an , A m J ou r of S cie nce,
v on
.
R
c
n,
J
C o te
o p e it
p
I
.
40 4
3
.
Pro fe or F
ss
ns t
.
i e
e t p
.
P
M in in g En g
ose p n
,
v ol
.
y,
T he G
xxiii
.
i o
ei
p 1 97
.
k
e e i of
n s s
.
.
.
p og e
.
O re
.
D epo s its
t te bo t p i g
vol xxv
.
,
T r a ns
A m ee
zc a n
'
'
.
.
D EP O S I T S
O RE
G E
N ET I CAL LY C O N S I D ER ED
12 1
.
h
s rin
e vidence of v e in
by
o
t
Th e y hav e b ee n
g
p
g action
1
2
fully d e scrib e d by L e Conte Beck e r and o th e r wri te rs
I n a valley surrounded w it h e rup ti v e rock s and u nd e rlain by
al te r e d s e d i m e n taries b e liev e d to b e of arch aean age t herma l
s prings issu e from s e v e ral po i nts from no rth a n d sou t h fi s s u r e s
Th e fl oor of t he vall e y is cov e r e d i n plac e s wi t h a sh ee t of
ca lcareous s in t er in which t h e r e ar e many fi ss u re s h e r e and t h e r e
still op e n bu t mos tly cl os e d by t he d e pos it of sil i ca on th ei r wall s
F rom som e of t he sp rin gs hot vapours and gases c h ic fly COQ
s
t
ill
i
s
a nd H S
s ue
2
Beck e r fo u nd in th e mineral water small amoun ts of m e rcury
sulphi de and sod ium sulphide
About a mil e to t he w e st of th e ma in group t h e r e are similar
fiss u r e s yield i ng s t ea m and C O
I n th e s i n ters of t h e s e occur
s e v e ral m e tallic s ulphid e s
Beck e r analys e d t he fillin g of s e v e ral fis s u re s and fo u nd
b e si des hydra te d fe rric ox i d e l e ad copper and m e rcury s ulphid e s
gold and silver a n d t rac e s of zinc man g an e se cobal t a n d n i ck e l
The occ ur renc e of m e tall i c sulphid e s i n t he s i n ters a t Sulphur
Bank Stea mb oa t Springs a n d O ha e awai Hot Spring s ; th e
mushroom capped lod e s a t Wa i hi and G r e a t Barri e r I slan d ; t h e
t r ee stems replac ed by sulphides found in v e ins a t gr e a t d e p th s
below th e pres e nt su rfac e afford conclusiv e e vid e nc e of th e fi llin g
of veins by hot asc e nding wa ters and gas e s in areas occupi e d by
late e r uptiv e rocks
It is a no torious circums ta nc e t ha t ore depos its are mo s t
common i n the n ei ghbourhood of e xt e nded zones of ign eous rocks
as in Hungary Transyl v ania Ne vad a Colo r ado and Ne w Zealand
wher e th e v e in b e ar i ng rocks ar e pr i ncipall y andesi te phonol ite
and t rachyte
I n o ther rocks vein s ar e f e w e r and mor e s c a t ter ed
F or v ei ns in th e alt e r e d la ter e ruptiv e s L i ndgr e n s ugg e s ts th e
nam e propyl i te v e ins bu t i t is doub t ful whether t h e g e n et ic
diff er e nc e b e tw ee n t h e m and t ru e fi ss u r e v e in s is s u ffi c ie n t ly
marked to j ustify th e d i s tinction M or e ov e r t h e roo ts of propyl i te
v e ins would be diffi c u l t to distingu i s h from fi ss ur e v ei ns conn e cte d
w it h a plu ton i c intrusion
3
Profe ss or S u ess speaking of t he impo rta nc e of th e 1 01e
played by th e wan i ng phases of volcanic phenom e na in t h e
forma ti on of mineral v e ins says Ho t springs may b e tak e n as
C onte O M i ner l Vein w ”i Progre t S tea m b t S pri g
J L
o m p red with th am e t S lph r B a k A m J r f S n
l xxv
—fi ll in
r
.
,
,
.
,
,
.
,
,
,
,
,
.
,
,
.
,
,
.
.
,
,
,
,
,
,
,
,
,
.
,
,
-
-
,
,
.
-
.
,
,
,
,
,
,
-
,
,
.
.
-
,
-
.
,
-
.
'
,
“
-
,
,
1
e
.
c
n
,
a
e
s
a
u
n
s no
a
u
n
ss a
.
,
ou
.
n
oa
o
cze
ce , v o
.
p 424
3
G l y f th e Qu c s l v r D e s s f th e P
G
F B c r,
ash n n , 1888, p 3 3 1
S l p , U S G eo l S u rv ey ,
3
r f ss r Edwa rd S u ss , L c ur s , T he G eog r ap h ic a l J ou rn a l , v ol
N ov 1 90 2 , p 5 2 0
.
.
.
o e
Poe o
.
.
e ke
.
.
eo og o
W i gto
e
et e
.
.
.
iki e
.
s
po it o
.
.
.
a c ifi c
xx
.
,
12 2
MININ G GEOLOGY
.
the latest phases of a whol e seri e s which led up to th e pr e sent
”
deposits of ore
A c tion of a scend ing A lka line Wa ter s — Th e wat e rs wh i ch r i s e to
the surfac e in th e r e g i on about L ak e Rotorua ar e alkalin e neu t ral or
acid Shafts and bor e ho l e s pu t down in th e pum i c e a n d rhyoli tes
which constitute th e great b u lk of the rocks in this ar e a hav e shown
that th e alkalin e waters come from a d e ep seated sourc e whil e th e
acid wat e rs hav e quite a s u pe rfi c ia l origin This has l e d to th e
erron e ous conclusion that all the wa t er s have not a common origin
L ake Rotorua is an old crater lak e the southern shor e s of which
are crus t ed ov e r with deposits of s i nt e r formed by the exis t ing hot
springs Below the sinter ther e is a thick deposit of pumic e and
below th e pumic e fl o ws of rhyolite g e nerally pum i c e ous or p i solitic
I n th e pumic e ther e ar e m a n y de pos its of fi n e ly diss e m i nated
marcasite which were apparently formed by solfatari c action at
some e arlier dat e in th e way t hat th e d e posits of pyrit e s and
cinnabar are now being formed at O ha e awai Hot Springs nor t h
of Auckland
The hot ascend i ng alkaline chlorinated waters
becom e partially or wholly oxid i s e d into sulphates by contact with
the decomposing iron sulphid e with forma t ion of free sulphuric
and hydrochloric acids and liberation of sulphurett e d hy drogen
and sulphurous acids I n this way the ascending alkaline waters
that happen to com e in contact wi t h masses of pyrites b e com e
oxidised in t h e superficial laye rs of th e pumice and ris e to the
surfac e as neutral or acid springs according to the d e gree of oxida
tion th ey have u n dergone
Thus within a small ar e a we have the sing u lar phenom e non of
waters that r e ach the surface in all conditions ra n ging from the
highly alkaline to th e ex t r e mely acid according to the degree of
oxidation of the contain e d salts
1
Th e composition of the salts in the alkaline waters of Ra c h e l
Spring in grains p e r gallon is as follows
Sodium chlorid e
Potassium chlor i d e
L ithium chlorid e
Sodium s u lphat e
Silica
Sodium silicat e
Calc i um silica te
M agn e sium silicate
O xides of iron and alumina
Total
.
,
,
-
.
,
,
-
,
.
.
-
,
.
,
.
'
,
,
.
,
.
,
.
,
.
,
,
,
,
,
,
,
,
,
,
T h e M ine ra l Wa ters
a r I , 190 4,
3
9
p
1
P t
.
.
.
a nd
H ea lth Resorts of N ew Z
ea la nd ,
Dr Woh l mann
,
D EP O S I T S
OR E
N ET I C ALLY C O NS I D E R E D
G E
12 3
.
Also sul phur ett ed hydrog e n and carbon dioxi de no t estimated
I n th e major ity of c a s e s th e alkal i n e spr i ngs d e pos it lay e rs of
s i lica on th e walls of th e v e n t and at th e su r fac e th e latte r ofte n
form i ng larg e mushroom shap e d mass e s
Th e composi t ion of th e wat e rs of th e Pri e st ho t spring wh i ch
may b e tak e n as typical of th e acid wate rs is as follows
G rai ns pe r g allo n
Sulphate of soda
po tash
trac e s
lime
magn e s i a
alum i na
iron
Sulphur i c acid (free )
Hy drochloric acid (free )
S i lica
.
,
,
-
.
,
,
.
,
,
,
,
,
,
,
,
,
96 7 7
Th e t e mperature of the alkal i n e wa te rs as their de e p seat e d
o rig i n would sugg e s t is very high varying from 180 to 2 1 2
Fahr
whil e tha t of the acid wat e rs is low commonly ranging
from 98 to 1 10 F ahr
The sinte rs are found of all degrees of ha rdn e s s Th ey ar e
soft spongy and v e sicular or hard and compact Th e sin te r
encrus t i n g the walls of t h e fi ss u re s and pip e s from which th e
wat e rs escap e at th e sur fac e is generally hard and chalc e donic
a n d arrang e d in laye rs wh i ch often present a fi n e ribbon s t ructur e
Hand sp e cim e ns of the hard e r sint e rs canno t b e
from much of th e o r e found a t t h e outc rop of th e
Martha lod e at Waihi I n pl a c e s t h e s i nt e rs conta i n fi n e ly d i s
sem i nated marcasit e and a t rac e of gol d and s i lv e r
Around Roto rua we can see or e d e pos its of th e solfa ta ric clas s
still in process of formation on a scal e of consid e rable magn i tud e
O f th e genesis of the ascending alkal i n e waters nothing is known
at pre s e nt
6
I n this class ar e group e d d e posi ts of s ulph ur
( ) F u m a ro l ic
f e rr i c chlorid e cupric oxid e and boron sal t s forme d by t h e e scap e
of steam and gas e ous emanations in volcan i c r e gions O f th e se
sulphur and boric acid alone ar e of economic value
Boron salts are common in many vol can i c reg i ons Th e ent i r e
production of boric ac i d from Ita ly is ob ta i n e d from t h e s te am
fumarol e s in th e provinc e s of Pisa a n d G rosse to
Sulphur is subl i m e d from fumarol e s and crat e rs by t h e mutual
r eac t ion of hydrog e n s u lphide and sulphur d io xid e I t is found
-
,
°
°
,
,
,
°
°
.
.
,
,
,
.
-
.
.
.
.
.
-
,
.
,
,
,
.
.
.
.
.
,
124
MININ G GEOLO G Y
.
impregnating vesicular lavas tufts and sili c eous sinters and mix e d
wi th volcanic muds and gypsum deposits
Th e most important known d e posits of sulphur occur in Italy
Spa i n Hungary Chili Me xico Japan Uni te d S tat e s and Ne w
Zealand
The sulphur—d e posits of I taly occur in veins or len t icular
masses in rocks of Mi ocene ag e c h ie fly in the provinces of
Cal tan i setta and G irg e nti
I n N evada the sulphur b e aring rock oc c u rs in b e ds lying
b e twe e n limeston e and magnesian rocks
111 Utah th e sulphur occurs associat e d with gypsum near an
old crater
A t Tiki te r e in N ew Zealand th e re are e xt e nsive deposits of
sulphur in an old crat e r A large proportion of the sulphur is
th e black amorphous variety The heat of the fumaroles and hot
S prings is too gr e at to permit the excavation of the sulphur to a
gr e at e r depth than 6 or 8 feet
A t Whit e I sland th e d e posits of sulphur occur in and around
th e crater lake mixed with gypsum The crat e r water is ho t
and highly charged with free hydrochloric and sulphuric acids
Th e gypsum is deposit e d in crystall i n e incrustations on the sides
and fl oor of the cra t er lak e The sourc e of the lime has not y e t
be e n d e termine d ; but the supply must be constant as gypsum i s
b e ing deposi t ed continuously
The sulphur is depos i ted in the wat e r from gas springs which
are s e en bubbling e verywhere in th e fl oor of the lake and also
from fumarol e s around th e margin of the crater
—
A
6 ) C o n t a c t M e ta m o r h ic
D
o
molten
magma
e
s
i
t
s
p
(
p
t e n ds to e ffe ct changes in th e rocks with which i t com e s in
contact I n th e case of ov e rfl o w magmas the thermal chang e s
ar e g e nerally t r ifl in g and in many cases hardly appr e c i abl e
E v e n magmas tha t hav e cool e d in r e nts in sedimen t ari e s at
shallow d e pths hav e not al ways caus e d great chang e s in the
enclosing rock
The gr e at e st alteration will naturally tak e plac e in the case of
magmas that do not reach t h e surfac e but cool slowly under
gr e at pr e ssure
Th e gr e a t er the mass of the intrusive magma th e slow e r wil l
b e the rat e of cooling ; and th e slow e r the rate of cooling the
long e r will th e adj acent rocks b e h e at e d
Th e rate of cooling will be mainly dependent upon the mass
of the i ntr usion th e dis tance from the su rface a n d the rela ti v e
thermal conductivity of the adjac e nt rocks
The changes effect e d in the country rock by the intrusion of an
igneous magma will be mechanical and thermal
,
,
,
.
,
,
,
,
,
,
,
.
,
,
.
-
,
.
,
,
.
,
,
.
.
.
,
-
-
,
,
.
.
,
-
.
,
.
-
,
.
.
,
.
,
.
,
.
,
,
,
.
,
,
.
,
,
.
-
.
12 6
MININ G GEOLOGY
.
I t is probable that t he cir c ulation of the heated mineralised
solutions in the later phases will t e nd to effe c t a redistribution of
the ores and minerals d e pos i t e d in the e arlier stages I n some cases
t he ascending wa te rs and gases may reach the zon e of surface
circula ti on and mix wi th t he met e oric waters which may then
reapp e ar as hot springs forming ore bodies and v e ins not directly
in con tact w i th th e eruptive magma
W ee d and som e oth e r wri te rs have made an attempt to
i nto groups dep e nding
s ub di v id e conta c t metamorphic deposits
,
,
,
.
,
,
-
,
.
-
,
mainly upon the mode of occurrence B u t the form and mode of
d i s t ribut i on may be du e to accid e n t s of de n sity or porosity
composition and hydrous condition of the rocks a ffecte d rather
than d i ffe r e nces in genetic formation
M oreover the mass of the magma the weight of s u pe rin c u m
b e n t rocks t he amount of hea t and subsequent contraction a n d
phase of t he af t er action are all doub tless contr i buting factors in
connection with the form and distr i bution of th e heavy metals
M asses of ore occurring as contact—depos i ts fiss u re v e ins and
bed impr e gnations in the zon e of metamorphism may all be t raced
t o the same gen e tic caus e s
Professor L de L aunay of Paris supports the vi e ws of the school
of D e Beaumont and D au b r e e i n respect of th e primary in fl u e n c e of
volatil e m i neral i se rs emanating from eruptive magmas The emana
t i ons he contends must have prepar e d th e way by in t roducing into
t he enclos i ng rocks or simply by deposit i ng in the vein fi ss u r e s
const i tuents such as sulphid e s fl u or ide s chlor i des etc which s u b s e
qu e ntly dissolv e d ane w by th e circulation of s u p e r fi c ia l wat e rs hav e
1
rend e red the latter essential aid in th e proc e sses of al t eration
The extent of contact me tamorph i sm e ff e cted by the granite
intrusions of Albany i n N ew Hampshir e was fully i nv e stigat e d by
2
Hawes
His analyses show e d a progr e ss i ve series of changes in
the schists as th e y approach th e gran i te
The rocks are de
hydrat e d boric a n d silicic ac i ds have be e n added to them and
there appears to have b e en an inf u sion of alkal i at the time of
contact He regarded th e schists as having been impr e gnat e d by
hot vapours and solut i ons emanating from t h e grani te
Contact deposi t s frequently lie at th e boun dary b e tween the
erupt i ve and the country ro c k ; also at variable distances from
t he e ruptive but nev e r outsid e th e zone of metamorph i sm
M ore par ti cularly conta c t ores occur in limeston e s ma rly and
clay slat e s a n d are accompanied by the usual c ontact min e ral s
garn e t v e suvianit e scapolite wollastonit e aug i te m ica horn
bl e nd e e tc and in clay slat e by chiastol i te e tc
L de L a u n a y T he G e nesis of Or e D ep os its 1 90 1 D i sc u ss io n p 6 1 6
3
G W Hawes A me r J o u r n S c i xx i 1 88 1 p 2 1
.
,
,
.
,
,
,
,
-
,
.
-
,
,
,
-
,
,
.
,
.
,
.
,
,
,
-
,
,
,
,
,
.
,
,
,
.
-
,
,
.
.
,
,
.
.
-
-
,
.
-
,
,
-
-
,
,
,
,
,
,
,
,
-
,
.
,
.
,
1
.
.
,
.
,
.
.
,
.
,
,
,
,
,
.
.
.
.
O RE
D EP O S IT S
G E
N ET I C ALLY C O N S I D ERED
12 7
.
Contact ores ar e pr i nc i pa lly magn etit e a n d spec ular i ron bu t
sulphi de s of copp e r l e ad a n d zinc oft en oc cur
con tact d e pos its ar e typ i cally repr e s e nte d by t h ose of
in N orway R i o Tinto Tharsis and San D omin go i n
Spa i n
Th e pyr it i c or e mass i n M oun t L yell M ine i n Tas mania is
g e n e rally d e scrib e d as a r e plac e m e n t conta c t —d e pos it al though its
g eo log i c occurr e nc e d oes no t s trj c tly conform t o t h e co m mon de fi
n it io n of such a body
Prof e s s or G r e gory d esc r i bes i t as a b oa t
1
shap e d mass ly i ng b et w ee n talcos e sch i s t a n d conglom e ra te s
Th e m i ne worki ngs hav e shown t hat i t gradually t ape rs down
wards from the ou t crop b ei ng cu t o ff w it h a rounded base by a
gr e a t t hr us t plane ( too a t )
There ar e no eruptiv e s i n ac t ual c on tac t w it h t he or e body
bu t dykes of d i abase and o ther i gn eous rocks occur in t h e dis t ri c t
a t no gr e at distanc e Th e pr e s e nc e of t h e s e dyk e s and of ban d s
of sch i s t i mpr e gna t ed w it h sulphides forming fahlbands woul d
lead to t he b e lie f tha t a t o ne ti m e ther e ex i s t ed chann e ls of com
m u n ica t ion l e ad i ng from the e ru p ti v e magma s to t h e v e in cavi tie s
I n all p robab i l ity th e M oun t Lyell sul ph i de ore bod ie s a n d be d
impregna ti ons were forme d in t h e la ter or solfata r i c s ta ges of
e rup ti ve aft e r ac t ions
—
d
o
M
o
D
o
To
t
h
i
s
group
i
R
e
l
r
h
i
s
i
n
a
e
t
a
m
c
e
s
t
( )
p
g
p
belong t he d e posi ts of iron o r e which occur i n al tered sed i
m e n t ary rocks g e n e rally of old e r Pal aeozoic age
Th e i ron probably ex i sted or i gi nally as sed i men tary d e posi ts
and b e cam e conc e n t ra t e d a n d r e arrang e d und e r the in fl u e n c e of
th e h ea t pressur e and solu t ions wh i c h caused the me tamorph i sm
of t he enclos i ng rocks
E xampl e s of d epos i ts of ore due to regional m e tamo rph i sm i n
wh i ch m e tasoma ti c proc e ss e s doub tl e ss took an activ e pa rt ar e
foun d among t h e valuable magnet i c d e pos i t s of Swe d en and t h e
vas t specular iron and magn etite mass e s of M ich i gan
Mass i v e aggr e ga te s of magne tite ar e common i n chlori t e schis t
and m i ca sch i st in all par t s of t h e globe
Metamorph i c rocks also e nclos e be d s of iron pyri te s and pyr
r h ot it e t h e or i gin of which is st i ll obscur e
-
,
,
,
.
-
,
,
,
,
.
-
,
,
,
.
.
,
-
,
-
”
.
-
,
,
,
.
,
,
,
-
.
-
,
,
-
.
.
-
.
,
,
,
,
,
.
,
,
.
-
-
.
,
.
III — M E T E O R I C WA T ERS
—
a
C
l
I
this
group
are
i
nclud
e
d
d
e
posits
of
sal
t
n
h
m
i
e
c
a
( )
borax nitr e bog i ron ore and some d e pos it s of gypsum a n d
mangan e s e
”
P ro fe or J W G regory T h M o nt Lyell Mi i ng F iel d T
A u t
I
t Mi
E
l 1 Part I V J ly 1 90 4 p 2 8 1
.
.
,
.
,
-
,
,
.
1
ns
ss
.
n
.
“
.
vo
.
.
.
,
n
u
e
,
u
,
.
.
,
r a ns
.
s
.
128
MININ G GEOL OGY
.
—
b
M
l
n
i
ca
e ch a
( )
This group includ e s all sedimentary ro ck s
form e d by th e ag e ncy of water i n lak e s and seas also alluv ial
drift s wh e th e r loose or compac t of river or lake origin con tai n
ing gol d t i n pla t inum a n d g e ms and ore bear i ng
d e posi t s
.
,
,
,
-
,
,
,
.
IV
.
—
OR G A N I C
.
—
1 o u p e mbraces all vari e ti e s of
V
l
This
61
b
e
t
a
e
e
g
( )
g
fuel rang ing f1 o m peat t o an thrac i te also graph i te 0 11 shal e
m i n e ral o i l and natural gas
—
l
The m i nerals i nclud e d in t his subdivision are
A n im a
l im e stone s including chalk and m i n e ral phosphates
.
,
,
,
.
,
.
,
.
1 30
MININ G GEOLOGY
.
belonging to the fi r st group are i n frequent and
therefore economically subordinat e in impo rtanc e to those of the
se c ond group They include according to Vogt
O re -deposits
,
,
.
( )
a
The o c currences of titani c iron ores in basi c and semi basi c
eruptives
Chromite in peridotite
S ulphide deposits i n c luding the ni c keliferous py r rhotite of
Sudbury in Canada
Platinum metals in highly basic eruptive ro c ks
Copper and metalli c ni c kel iron in serpentinised peridotite
-
.
( b)
( )
c
.
,
.
,
d
( )
()
e
-
.
.
That sulphides c a n be segregat e d from e ruptive magmas in the
firs t conc e ntration has yet to b e proved and it is still doubtful
how far V ogt s c onclusions respe c ting the occurrence of sulphide
or e as a product of primary segregation from a molten magma
a re admissibl e
I n all cases metasomati c pro c esses a re sa id to have played an
important part in th e formation of these valuable depos i ts
111 the e ruptive after action group V ogt i n c ludes cassiterite
”
and apat ite veins and ore deposits of contact metamorphic zone
Cassiterite deposits are everywhere conne c ted with acid crup
t iv e s principally granite and oc c asionally qu a rt z po rphyry and
rhyolite Partly for this reason and partly because of the
chara c teristi c paragen e sis of fl u or ide bora t e and phosphate
minerals he supports the common view that tin deposits are
genetically connect e d with granitic eruptions a n d that various
volatile fl u oride s took part in th e ir formation
Cassiterit e veins were forme d he thinks by p neu matoly tic
1
that is by the action of gases and water at high
p ro cesses
t emperature and pressure
H e further urges that they were formed immediately after the
eruption and before t he c omplete cooling of the granite one
proof o f which h e thinks is the o cc urren c e of tin vein mine rals in
veins of pegmatite in th e granite
Cassiter it e veins are admittedly independent of the immediately
adj acent country rock and for t his r e ason seem to be mo r e nearly
related to deposits of magmatic s e gregation than to conta c t meta
morphi c d e pos i ts
I t is probable that the magmatic segregation of chromite in
peridotite was in some cases e ffe ct e d by pneumatolytic agencies
b e fore the complete cooling of the magma It i s not uncommon
to h n d chromi t e in v ei n like masses that have the appearan c e of
hav i ng be e n segregat e d i n cavit i es of c ontra c tion in the pasty
Pn eumatoly s i s is a term firs t u sed by B unsen to describe th e c ombi ned
actio n o f gases a nd water
’
,
,
.
.
-
,
-
-
.
-
,
,
,
.
,
,
-
,
,
.
,
,
,
,
.
,
,
-
,
,
.
-
,
-
.
.
-
1
.
T
H EO R I ES
F O RM AT I O N
o r V E IN
1 31
.
magma As the agency of unde rground wate r cannot hav e been
act i v e i n this class of ore d e posit t he aggregat i on must hav e be e n
e ffected by metal bearing s t eam and gas e s occluded i n th e igneous
.
-
,
-
P e gmatite veins while generally conne c ted w i th grani t ic
e ru p ti ons s ee m to be of lat e r format i on than the ca ssiterite veins
They often pass into quartz a n d frequently possess sha rp w e ll
de fin e d walls wh i ch suggest the ir forf na tion i n shr i nkag e cracks
by p n e u m a toh y da to gene t ic ag e ncies in t he wan i ng phas e s of t h e
aft er act i ons d ev e loped by th e progress i v e cool i ng of t he eru p ti ve
ma gma Teall h as sugg e sted that micrope gma tite is an eu t ec ti c
wh i ch crystallis e s at the lowest poss i bl e temperature a n d re
pr e s e nts i n c e rta i n rocks th e fi n a l mo t her l i quor from which th e
o th e r minerals have crystallis e d ou t
The di ffe r e n t phases of af t e r ac ti on must nec e ssar i ly m e rg e i n t o
each o ther and henc e we may e xpect to fin d as w e do ti n v e in
minerals and e v e n c a ss it erite in veins of pegma tite
Among ore —deposi t s of contact m e tamorph i c origin V ogt in
the or e bod i es wh i ch occur with in th e m e ta morphos e d
c lu de s
contact zon e of d ee p e ruptiv e s esp e c i ally grani te
Th e
He d i s t i ngu i shes s e veral typ e s of contact d eposit
Christian i a typ e i nclude s i ron or e d e pos i ts tha t appea r t o have
b e en formed befor e t h e solidifi ca tion of th e grani ti c magma
Th e se ores are n e ver foun d i n the gr ani te but al ways i n t he
adj acent rocks I f they h a d been introduced aft er th e cooling of
th e magm a they would also hav e been depo sit ed in th e granite
Th e eruptiv e magma i s b e l ie ved to be the sourc e of th e
me tal which is ex pelled in th e heated steam into t he surround
i ng rocks
1
I n 1 90 2 Weed proposed t h e following provisional g e n e t i c
c la ss ific a t ion bas e d on t ha t of V ogt
,
,
.
,
-
-
,
.
,
-
.
-
-
,
,
,
.
-
,
-
-
,
.
-
.
-
.
,
.
,
.
.
.
,
magmatic
s
e
gr
e
gation
)
(
S
i
liceous
a
( )
6
Bas
i
c
( )
11 I gneous ( e manation deposits )
Contact
m
e
tamorphic
d
e
posits
a
( )
V
eins
related
to
magmat
i
c
v
ei
ns
and
d
i
vis
i
on
IV
6
( )
(
III F umarolic
IV G as aqu e ous (pn e u m a toh yda to genetic) d e posits
Fi
lling
d
e
pos
i
ts
a
( )
Replacement
deposi
t
s
b
( )
1
T r a ns A
O re D epo s its near I gneo u s Co nta c ts
W H Weed
ns t M E
1 903 p 71 5
v ol xxx iii
L I g n e ou s
.
.
.
-
.
.
.
-
-
.
.
.
“
.
I
.
,
,
,
.
.
.
,
,
.
.
.
mer
.
1 32
MI N IN G GEO L OG Y
V
.
M eteoric waters
.
Underground
( )
6
u e r fi c ia l
S
p
( )
I n this c las s ifica tion the maj or subdivisions are based upon
magmatic segr egation at one end and cold a queous deposition at
the oth e r w i th i nt e rmediate groups chara c teristic of the diff e rent
phases of erup t ive after a c tions
Weed divides magmati c segregations into two groups namely
The latter embra c es deposits of iron c opper
S ili c eous and Basi c
found at igneous borde r s and as dykes and the former the
e tc
1
—
ore bear i ng pegmatites with quartz v e ins as extreme e xamples
This is a dist i nct departure from V ogt s con c eption of magmatic
segrega t ion I t is almo s t certa in that the segregation of ores
from basi c magmas and th e formation of cass i ter i te and pegmat i t e
ve i ns ar e genetically connected with the after act i ons of de e p
seated erup ti ons and as such must in some degree be relat e d and
merge into each other But this genetic conne c tion whil e i t
increases the diffi c u lty of formulating a satisfac t ory c la ss ific a t ion
ha rdly j u s tifie s th e subdivision proposed by Weed
Th e synthetic exper i ments of D au b re e seem to support the
views of V ogt Beck and other observ e rs who maintain t hat
cass i teri te a n d pegmatite veins are formed by gaseous and aque
ous e manat i ons and not by direct segregation
G ol d is commonly assoc i at e d with acid ro c ks but it do e s not
o cc ur in such a mann e r as to suggest dire c t segregat i on 111
Queenslan d Ne w South Wal e s and N ew Z e aland it i s found in
quartz v e ins i n granite and quartz porphyry but in these cas e s the
veins m anifestly fill contraction c ra c ks
Weed strongly dissents from the view expressed by Van Hise
that meteoric waters are an important creative fa c tor in the for
mation of ore veins He thinks however that primary hot ore
bear i ng solutions and hot vapours m a y rise into th e zone of
circulating meteoric wate rs heating the latt e r and charging th e m
with metall i c salts and such a c tive mineral solvents as fl u orin e
chlorine and bo ron He summarises his views relating to the
formation of contact deposits as follows
Contact metamorphic ore —deposits oc c ur about the margin
of intrusive masses of granular i gneous rock either at the actual
contact or in the zone of metamorphosed sedimentar i es The
depos i ts of e conom i c value oc c ur only where strata or blocks of
impur e limestone have been crystallis e d as garnet i f e rous or
act i nolite cal c ite rocks with cons e quent porosity
The ore
minerals are intimately associated with these alum i nous silicates
a
.
.
,
-
.
,
,
.
.
,
,
,
,
-
,
.
’
.
,
-
,
,
,
,
.
,
,
.
,
,
.
,
,
.
,
,
-
,
.
,
-
,
.
,
,
,
,
.
-
,
.
-
.
,
,
1
Weed
,
Z oe
.
cit”
p 7 17
.
.
1 34
MININ G GEOLOG Y
.
Th e latter do not compare with the fo rme r as an e ffi c ie n t
cause
—
According to this th e ory it
T h e o ry o f L a te ra l S e c re t io n
is assum e d that m e t e oric wat e rs percolating t hrough the c ountry
rock by the aid of carbon dioxid e and alkalies dissolve out
c ertain c onstituents which are afterwards d e posited in fissures
ther e by forming mineral veins
The origin of the theory is unknown but it is certai n that
D elius in 1 7 7 0 G e rh arde in 1 7 8 1 and L asius in 1 7 89 wer e
supporters of it th e latte r basing his conceptions u pon a c ar e ful
1
e xamination of the veins of th e Hartz mountains
I n 184 7 Professor Bischof of Bonn a distinguished geologi s t
—
t
and chemist in his fascinating T ex book of Che mica l a nd P h y sica l
G eolog y dis c usses the chemical processes which take plac e when
met e oric waters and different kinds of aqueous solutions com e in
conta c t with rocks His work crea t ed a new s c ie n tifi c basis of
r e sear c h in this branch of economi c geology He contended that
ores were obtained by leaching from th e rocks travers e d by th e
v e ins and suggested the possibility of the v e in constituents
being found in th e adj ace n t r ocks
I n 18 5 5 Forch h a m m e r th e famous chemist of Cop e nhagen
found traces of lead copper and zin c in the r oo fin g slates of
N orth Wales a discov e ry which was held to a ff ord conclusiv e
proof of the or i gin of ore v e ins by processes of lateral secretion
I n 18 7 3 Prof e ssor F S a n db e rg e r of Wurzburg dis sa tisfi e d with
the meagre results obtained from th e e xamination of sedimentary
rocks dir e cted his attention to a systematic chemical investigation
of the rocks t raversed by ore veins in difi e r e n t mining centres in
the Black F orest and of the v e in stuff itself
I n clay slate he discovered copper zinc l e ad arseni c antimony
t i n cobalt and nickel in sandstone lead and copper ; whil e
ti tanic and phosphori c acids were found to be present e verywher e
in small quant i ty
S a n db e rg e r s r e sults showed that a clos e r elationship exist e d
b e tween v e in contents and the country rock ; but he was by no
m e ans s a tis fi e d as to the origin of the heavy metals He accord
in g ly extend e d h i s investigation to an examina t ion of the con
s t itu e n t s of ign e ous ro c ks
He crushe d large samples of rock and separated the cons t ituent
minerals by solutions of different densities
Samples of th e
individual crystallised silicates thus isolated were subj ected to
and by this means w er e found all the usual
c areful analysis
elements p r esent in metall iferous v e ins
1
G eorge :Las i u s
O b servations on th e H artz M ounta ins Ores a nd
M in er a ls v ol ii Han o ve r 1 789
.
,
.
,
,
,
-
.
,
,
,
,
,
.
,
,
,
,
,
.
.
-
,
.
,
,
,
,
,
,
-
.
.
,
,
,
,
-
-
,
.
-
,
,
,
,
,
,
,
.
’
-
-
.
.
.
,
.
,
,
.
.
,
,
,
.
,
O I
T H E R ES
O F V E IN
F O RM A T I O N
1 35
.
Thus in olivin e h e foun d iron nickel c opp e r and cobalt in
aug it e coppe r cobalt i ron n i ck e l lead ti n a n d z i nc ; and in t h e
m i cas many bas e metals Gol d mercury and tellurium were not
sought for
I n 1880 S a n db e rg e r announced his beli e f that t he mineral
con t en t s of veins w e r e d e r i v e d not from some unknown d e pth
but from the immediat e wall rock
G old b e aring v ei ns are common in slates and sandstones of
marin e origin and as s e a wa te i according to the announcem e nt
of S on s ta dt in 18 7 2 and of Profe s sor L iv e rs e dg e i n 1 893 con tains
according t o th e la tte r amounts ranging from 0 5 4 to 1 grain to
t h e ton it is held by the exponents of lateral se c r e tion t hat the
sea is t h e r e for e t h e source of th e gold in veins trave rsing ma rin e
s e dimentari e s
I t is ma i nta i ned that wh e n sedimen ts are formed on the fl oo r
of the sea t h e y must nec e ssarily e n t angl e a c e rtain propo rtion of
s e a water and t hat when these s e dim e n ts b e com e consol i dated
th e gold must r e ma i n in th e m
Th e theory of lat e ral secre t ion received a n e w impulse from th e
res e arch e s of S a n db e rg e r I t seem e d compet e n t to e xplain t h e
origin of many ore—v e ins and although strongly opposed by
Prof e ssor S te lz n e r of F r ei b e rg and Professor P os e pn y of P r z i
bram it found much support in America in a mor e or less
m od ifi e d form
Thus E mmons 1 discus s ing t he manner in which he consid e rs
t h e L e adv i lle ore —d e pos i ts w e r e prod uced summari s es his vi e ws
0 11 ore formation in g e n e ral as follows
( 1) O r e d e posi ts hav e b e en d e pos ited from solu ti on rar e ly in
op e n cavi ti es mos t fr e qu e ntly by metasoma t ic interchang e
2
( ) Solu ti ons do not n e c e ssar i ly come dir e c t ly upwa rd s bu t
simply follow th e e as ie st chann e ls of approach
3
( ) Th e mat e rial was d e rived from sourc e s with i n limited and
conc e ivabl e d i sta nc e v e ry ofte n the older in t rus i v e r ocks
E mmons while s upporting th e principle of lateral s e cr e tion
disclaims th e narrow views of S a n db e rg e r who limi t ed t h e sourc e
of the ve i n con te n ts to th e wall rock i n immediate conta ct with
2
the vein
I n th e cri t ical discussion which follow e d th e publica tion of
”
“
Professor P os e pn y s paper 0 11 The G enesis of Ore D epos i ts i n
18 93 Blake a n d W i nslow r e a ffi rm ed their b e lief t hat t he z i nc and
3
lead ores of Wiscons i n were form e d by lateral secret i on
”
1
T r a ns A m
S
F E m m o ns
T h e G enes i s o f Certain O re D epo s its
,
,
,
,
,
,
,
.
,
,
,
,
,
.
,
,
,
-
.
-
'
-
,
,
,
,
,
,
,
,
.
,
.
.
,
,
,
,
,
,
.
,
,
-
-
,
.
,
,
.
.
,
,
,
,
-
-
.
’
,
,
-
.
“
.
I
ns t
.
3
3
.
M E
.
T he
L oc
.
,
,
v ol
xxx
p 12 5
G e n es is of Ore D eposits , 1 90 1 , p 1 99
cit ,
p 1 88
.
,
.
.
.
.
.
.
.
.
.
.
.
1 36
MI N IN G GEOLOGY
.
Becker whil e strongly dissenting from P ose pny s view that
metasomatic repla c ement was inc apable of producing such pro
n o u n c e d ore bodies as those at L eadville makes a clea r statement
of the supposed operation of metasomatic proc e sses He says
Replacement like solution must o c cur along fi ss u r e s or channels
and metasomatic ore bodies will present analogies in form to th e
Open spaces of caves of solution ( loo cit p
Rickard dis c usses the problem of ore fo r mation from a wide
standpoint and is n ot a dogmatic suppo r te r of the ext r e me doc
1
trines of e ither as c e n sion or late ral se cr etion
He a ffi rm s that
there is n o ground for the belief in the existen c e of a r ese rvoir of
water at g reat depth and maintains that all ascending water
must at one tim e have been desce n ding water
This last ca n only be true in regard to meteoric wate rs S o far
as the existen c e of deep seat e d water is c once rned his view is not
in accord with the hydro—fusion theory of modern petrologists
Rickard poss e ssing a personal knowledge of the g oldfi elds of
Australia and Ne w Zealand discusses the probable orig i n of the
veins of the Thames g oldfi e ld in the latter country ; and in the
main agrees with Captain H utton that th e y were formed by pro
cesses of lateral secretion by th e rmal waters
Professor J L e Conte i n a carefully prepared thesis combats
the extreme views of both P os e p ny and S a n db e rg e r (toe c it p
He makes an earnest attempt to combine what is true in
each a n d reconcile their di ff erences I t is manifest however
that h e leans favourably to the sid e of lateral se c retion processes
al though not de fin e d as such
He conside rs both sid e s partly right a n d both pa r tly w ro n g
Asce n sionists he thinks are righ t in de riving metals mainly
by as c ending solutions from great depths but wrong in imagin
ing th e se depths to be an exceptionally metalliferous barysphere
and wrong in not allowing subordinate contributio n s by lat e ral
curr e nts from t h e wall rock high e r u p
The lateral s e cre tion is ts on the othe r hand are right he thinks
in deriving metals by l eaching from the wall ro ck but wrong in
not making the thermospher e the main source
L e Conte succinctly summarise s his views in the following
terms
’
,
-
,
,
.
,
,
,
-
.
,
.
-
,
.
,
.
.
-
,
.
,
,
.
,
,
'
.
,
,
.
.
,
.
,
,
.
.
,
,
,
,
-
.
-
,
,
,
,
-
,
.
'
deposits using the term in its widest sense may tak e
pla c e from many kinds of waters but especially from
alkalin e solutions ; for these are the natural solvents of
metallic sulphides and metalli c sulphides are usually the
original form of such deposits
re
1
O
( )
-
,
,
,
,
.
1
L
oc
.
cit. ,
1
90
pp
.
a nd
2 11
.
1 38
MININ G GEOLOGY
.
cha ra c te rs are certainly due t o the e fi e c t of descending
waters
8
That
the
maj
ority
of
ore
deposits
if
not
all
are
partly
( )
deposited in pre existing op e nings and are partly replace
m e nts of wall rocks
'
.
-
,
,
-
,
-
.
From
the above he seems to attach too little importa nce to the
—
genetic connection existing between ore deposits and eruptive
processes and pla c es much dependence upon the formative power
of meteoric waters
1
Professor Ke m p contends that mining operations in America
show conclusively tha t mines become drier with incr e asing depth
and deep mining in South Africa Australia and N ew Zealand
adds con fi rm a tion to this view The dryness of mines in dep t h
seems to destroy the foundations of V an Hise s main contention
respecting the u nderground circulat i on of meteoric water
V an H i se admits that there are ore deposits which have a dir e ct
ign e ous origin but thinks they are of limit e d e xtent I n his
rej oinder to Kemp he seems to som e what modify his former con
c e p t ion with respect to the r 61e of meteori c waters in v e in forma
tion and admits that the ré l e of igneous intrusions may b e very
2
considerable
I t has b e en suggested by the oppon e nts of lateral secretion
that the m e tals contained in the silicat e minerals of eruptive rocks
ar e not primary but seconda ry consti t uents According to t h e ir
vie w lat e ral s e c r e tion is only a process of concentration
A s c e ns io n O f S o lu tio ns — Accor ding to this theory i t i s
assumed that the material whi c h fills a lode has b e en brought in
solutio n from gr e at depths and not from th e rocks in th e immediat e
vicinity of the lode
I n his classic memoir on T h e G enesis of Or e D ep osits the
late P r ofessor P os e pn y an ardent su pporter of the as c ension hypo
thesis laid great stress upon the occurren c e of sulphur and
cinnabar at S ulphu r Bank impregnating a de c omposed basalt and
still mildly in pro c ess of formation from gaseous emanations and
hot mineral waters
Similar con ditions exist at S tea m boat S prings in West e rn
N evada wh e re we hav e an exampl e of a mineral vein in proc e ss
of formation The matrix is banded siliceous ve i n stone conta i n
ing iron and copper sulphid e s sulphur and metall i c gold
S a n db e rg e r who was an equally strenuous supporter of lateral
se c retion obj e c ted to this view on the ground that he knew of no
.
,
,
.
’
.
-
,
.
-
,
.
,
,
.
,
.
,
.
,
.
,
,
,
,
.
,
-
.
.
,
,
,
,
,
Ke p
o Aq eo
ok
m ,
u
u s R c s in th e
J F
T h e R6l e f
T h e G en es is of Or e D ep os its , 1 90 1 , p 6 8 1
3
s , T h e G en e sis of Or e D ep os its , 1 90 1 ,
C R Va n
1
.
.
.
.
“
Hi e
.
.
F ormatio n
o f Vei n
D i scu ss ion
p 76 3
,
.
.
s,
O I
T H E R ES
FO R M AT I O N
or VEI N
1 39
.
spring which deposited mineral incrusta t ions on the walls of t h e ir
chann e ls He regarded t h e Sulphur Ban k and Steamboat Sp rings
phenomena as exceptional
Becker who made a special examination of the d e po sits at
Sulphu r Bank a n d S t eamboat Springs s t rongly opposed t he views
of t he ex t rem e asc e n sionists And wi t h r e ga rd t o the orig i n of
“
—
the deposits he e xpr e ss e d th e following views
Th e ev i d e nce
is ov e rwhelming that t he cinn a bar pyr i te and gold of the quick
s i lver mines of t h e P a c ific slop e r e ached t he i r present pos it io n s
in hot solutions of doubl e s u lphid e s which w e re leached out fr om
”1
masses underlying th e gran i t e and th e grani t e its elf
F u rt h e r
“
on h e says : I r e gard many of the gold vei ns of California as
having an origin entir e ly simila r to that of t he quicksilver
”
deposits
Beck e r s views postulate a new hypothesis which lies midway
betw ee n the as cension and lat e ral secre t ion theori e s and e xpresses
our pres e nt knowledge of ore—formation more nea rly than th e
e xtr e me views of P os e pn y and S a n db e rg e r
According to th e de fin it ion of la t eral secretion by the latter
t h e d e sc e n d ing wate rs b e ca me charg e d with mineral matter by
l e aching th e rocks in the region of vadose circulation O n the
oth e r hand P os e pn y ass umed tha t the asc e nding wa t ers b e cam e
charged a t gr e a t d e pths by coming in con ta c t w ith a de e p seated
b u t hypoth e tical repository of metalliferous ma t ter
Th e m odifi ca t ion sugg e s t ed by Becker favours the ascension
t h e ory and di ffers only from th e lateral s e cr et ion hypothesis in
assuming a d ee p e r sourc e for the mineral conte n ts of the v e in
matter
S u m m a ry — F rom t h e da ta r e co rd e d in th e pr e ceding pages
we may deduce the following conclusions r e spe c ting th e g e nesis of
ore deposi t s
.
.
,
,
.
,
,
,
,
.
.
’
,
-
,
.
,
.
,
-
.
‘
-
,
.
,
.
-
1
( )
That t he maj ority of ore d e posits are g e n e tically connect e d
with ign e ous i n t rusion s wh i ch may be plutonic or volcan i c
That c i rc u lating und e rgr ound wa ters a n d gas es are th e
princ i pal agents conc e rn e d i n t h e d i s s olu ti on primary
conc e ntration and deposition of vein ma tte r
Tha t ore—depo sits do not necessar i ly occupy pre e xisting
fi s s u r e s and cav itie s
That vein fillin g was in many cas es effected by metasomatic
repla c em e n t
That vein fi llin g waters are a scending waters bu t not
nec es sa r i ly d e ep—seated
-
.
(2)
,
-
.
,
3
( )
-
.
4
( )
-
.
5
( )
-
,
.
1
Sl
G
ope
.
,
Be ke
eo og o
Qu i ck s il ver
ograph xx iii ,
r, T h e G l y f t h e
F
c
U n ited S ta tes G eol S u r vey , M n
.
.
o
.
D epos its o f
th e P
1 8 88, p 44 9
.
.
ac ific
1 40
MININ G GEOLOGY
.
That the mine ral contents are d e rived from rocks contiguous
to the zone of fractur e or zone of metamorphism
That the accessory agents of dissolution are heat and
pressure aide d by dissolved alkaline minerals
That precipitation from th e asce n ding wat e rs tak e s plac e
in mor e or less o rd e rly hor i zontal zones in a cc ordance
wi th the laws governing solution a n d precipitation
That s e condary enri chm e nt is in the maj ority of cases due
to the migration of mineral c ontents from a high e r to a
lower level through the agency of des c ending m e teori c
waters
.
.
,
.
,
,
,
.
The theo ries of lateral secr e tion and as c ension of solutions are
based on the f u ndam e ntal assumption that the mineral matt e r
fi llin g cavities was deposited from circulating wate rs
Th e ir
d i fferenc e s lie principally in th e di ff erent c onceptions as to the
direction and operation of the circulating liquids
.
.
1
( )
The lateral —secretion theory supposes
a
i
c ending
That
th
e
n
of
cavities
was
the
work
of
des
fi
ll
( )
g
met e oric wate rs
6
That
the
matt
e
r
was
principally
obtain
fi
l
n
e d from
l
i
( )
g
the adj a c e nt rocks by a process of leachi n g
.
.
The asce n sion theory assumes
f
i
r c u la t
That
the
fi
l
i
n
of
veins
was
ef
e
cted
by
d
e
ep
l
c
)
g
(
ing wat e rs ascending t hrough open or partially
op e n fi ssu re s
b
That
th
e
mineral
and
metallic
contents
were
deriv
e
d
( )
—
from a de e p seat e d mineralised zon e
a
,
,
.
.
M any write rs assume that as c ending and descending wate rs
a re
merely units in what may be termed a hydraulic circ uit th e
interchange being caused by gravitation ass i sted by capillary act i on
and the difference of tempe rature of the ascending and d e scending
waters
M u c h of the mov e men t it is claimed is n e c essarily lateral a nd
towards channels fille d with ascending waters
I t was mainta i ned by Prof e ssor P os e pny and D r Raymond
that d e scending waters w e re mer e ly oxi dis i ng and incapabl e of
depositing sulphid e s Th i s contention has however be e n succ e ss
fully disproved by E mmons Becker V an Hise and other Am e rican
geologis t s who hav e shown the e xistence of s e condary sulph i d e s
both above and below water level or in what may be termed the
zone of vadose circulation
,
,
.
,
,
,
.
.
,
,
,
,
,
-
,
.
,
C H A P T ER VI I
O RES
.
A N D M I NE RA L S CONSI DE R E D
E C O N O M I CA L L Y
.
A l um i n i m
A nti mo ny A rseni c —A be to
A sph ltum Barytes Bi mu th Bor x Cement— C h rom i u m— Co l
— Cob lt— 0 0 pp — Cry o l ite D iam o n d
F i recl y
F l orite
G old
Graph ite
Gy p m
Iron Le d Mag e ite—M a gane e M i
O il S h le
Petro le m Pho ph ate R o k
N i ckel
M o ly bdenu m
—P l ti n m
S i lver
S late
T in
S l ph ur
T lc
Q i c ks i lve r
g ten — Z i
T
Al
CO N T E N T S
um
u
s
a
a
er
a
n
a
un
nc
s
s
u
u
u
u
n s
a
su
a
s
a
s
a
s
ca
c
s
u
a
.
mini n g student should possess a general knowledge of
the conditions under which the c ommonly useful ores a n d minerals
occur in N atur e and of the market condition quality and value
of the m i nerals inten ded for metallurgical and manufactur i ng
purposes
The market values are subj ect to cont i nual fl u c tu a t ion s and
the quotations given must be regarded more as a guide than a
standard of s e lling pri c es The min e rals and o r es are dealt with
in alphabeti c order
E VER Y
,
,
.
,
-
.
.
A LUM
.
The principal sou rc es of alum are alunite alum shales bauxite
and cryolite
A lu m te o c curs in veins and masses in eruptive rocks and for
the most part in acid lavas of later date in which it has probably
been formed by metasomatic replacement attending waning
solfataric action
A t Tolfa n e ar Civita V e cc hia in the neighbourhood of Rome it
occurs as thin irregular veins wh ich are supposed to have been
formed in contraction c racks by th e action of hot wate rs and
sulphurous gases upon the felspars of the containin g trachyte
A n important deposit of alunite oc c u rs at B u lla h de la h
M ountain in N e w South Wales I t c onsis t s of minerals rang i ng
from pu r e alunite to an impure form containing 4 0 per cent of
silica The deposit is over a m i le long nearly three qua rte rs of a
,
,
,
.
'
,
,
.
,
,
,
,
,
-
.
,
.
.
-
,
.
142
O RE S
A N D M IN ER
AL S CON S I D ERED E C O N O MI CA LLY
14 3
.
m ile wide and th e thickest band of stone varies from 6 0 to 7 0
yards wide I t is gen et ically connec ted with felsitic dyk e s which
t rav e rse Carboniferous slat e s The averag e compos it ion of t h e
mineral is as follows
,
,
.
.
Wat e r
Alumina
I ron oxide
Po tash
Sulphuric a c id
S i l i ca
,
,
,
,
,
,
Alum is obtained by calci n ing and washing aluni te a n d
evaporating the liquors
N atural alum is obtained in c ons i derable quanti t i e s in E ngland
and S cotland from the coal shales and alum c lays
Bauxi t e i s an i mpo rtant source of alum and aluminium sulpha t e
con
It
is
an
c entrated alum ) i n America F ranc e and G erma ny
(
aluminium iron hydra te — a n aluminous form of l i moni te — conta i n
i ng generally fr om 5 0 to 60 per cent of alumina
O f Am e ri can bauxi te from 65 to 7 0 per cent i s produc e d
in t he S tate of G eorgia and the balanc e i n Arkansas and
Alabama
The bauxite deposits i n the D epa rtment of Var in F rance are
mostly massive ooli ti c and c emented by carbona t e of l i me They
o c cur in old lak e b a s i ns extending westwa rd from Cannet du L uc
Th e or i gin of the mineral is still doubtful but by some w r ite rs i t
1s supposed t o hav e
b ee n genetically conn e c t e d w i t h solfata r i c
act i on i n and around t he anc i ent lak e s
A t Ba ux near Arle s t he bauxite occu rs ooli t ic and as gr ain s in
a compact l i mestone
O nly t h e varie t i e s of ba u xite free from iron oxide ca n be ut ilised
in the manufac t ur e of alum Th e purer grad e s are used for t he
preparat i on of aluminium hydrate from whi ch the metal aluminium
is man u fac tured
Cr y olzte another i mpo r tan t source of alum still continues to be
d e rived from th e min e s at I vigtut in G ree n land
Th e aluni te of Ne w South Wales is valued at abou t £ 3 per ton
The American domestic bauxi t e ranges in value from 1 4 8 to
1 8 8 per ton
F r e nch bauxite is d e l i v e r e d at Am e r i can seapo rt s
a t a somewhat lower rat e than the domestic mineral on accoun t of
the railroad freight charges
.
-
-
.
,
,
.
.
-
.
,
.
,
.
.
,
,
,
.
,
.
.
,
,
,
.
.
,
.
'
,
,
,
.
.
.
.
.
-
.
144
MIN I N G GEO L O G Y
A LU
M I N I UM
.
.
This metal is largely manufa c tur ed in G ermany A me r i c a and
F ran c e from bauxite principally produ c ed in the D epartment of
Var in S outhe r n F rance ( F or B a u xi te see
,
,
,
,
.
A N T I M ON Y
.
The only commercial ore of antimony is the sulphide antimonite
the oxides are secondary produ c ts found near the out c rop The
sulphide generally o cc u rs in veins in schist slate and sa ndston e
and also asso c iated to a small ex t ent with ores of lead bismuth
and copper
The principal produ c e rs of antimonite ar e F ran c e Alger i a I ta ly
M exico Turkey Hungary Ch i na and Canada Considerable
deposits o c cur in N ew South Wales and N ew Zealand but the ore
is generally of too low a grade to be payable
The ore must be very pure to be worth handling When u nde r
2 5 per c ent in the mine it is pra c tically impossible to separate the
ore from its gangue
Antimony ores are bought by smelters on a b asis of 45 per cent
of metal ea c h unit above that being pa i d for at s c hedule rate s
Und e r 4 5 per c ent there is a discount until the limit is reached
below which the or e has no commerc ial valu e E n glish smel te rs
do not care to tou c h ores containing unde r 4 0 p e r cent of metal
I n America an ore to be marketable must contain not less than
5 0 per cent of antimony
O res intended for the E ngl i sh market must be free from lead
arseni c c opper and zinc O n e per c ent of lead will r ende r the
ore unsaleabl e
The size of the ore also a ff e c ts the market val u e of the dr e ssed
mat e rial whi c h should not be b roken in pieces smaller than a
hazel nut
A n allowan c e is made for gold and silver when present in
s u ffi c ie n t quantity to pay f or extraction
The smelters payments
are based on the dry weight The percentage of m e tal shoul d b e
d e termined by the wet assay the fi re assay not being s u ffi c ie n tly
reliable
Antimony is mostly used for the manufacture of type metal
I ts value fl u ct u a t e s conside rably
,
,
.
,
,
,
,
.
,
,
,
,
,
,
.
,
,
.
.
.
.
-
.
,
.
,
.
.
.
.
,
.
.
,
,
,
.
.
.
,
-
.
’
.
.
,
.
-
.
A RS E N I C
.
The arsenious oxide of c omme rc e is manufactured from ars e nical
pyrites which is generally mined in association w ith o r es of gold
,
,
,
14 6
GEOLOGY
n un1 no
.
of rain wate r The lake contains no liquid asphalt N early
everywhe re the d e posit i s fi r m enough to walk upon
1
A c cording to M alo th e average compos i tion of the c rude
asphalt is as follows
-
.
.
.
,
The g reater part of the U nited States production is obtained
f rom bituminous sandstones in Califor n ia and Kentucky The
bituminous sandstone of California occurs in large qua n tities at
2
various points between San F ran c isco and L os Angeles
It
contains from 1 2 to 1 8 per c ent of bitumen the remainder being
quartz sa nd
The asphalt deposits of Kentucky oc c ur in n early horizontal
fi n e grai n ed sandstone belonging to the lower Carboniferous
.
.
,
.
-
.
-
p
e r iod
.
Bituminous limesto n es are the most important sou rc e of asphalt
in F ra nce Switzerland Cuba and the States of U tah Texas and
I ndian Territory in the U nited States
The Val de Travers mine at N eu c h atel in Switzerlan d and
the S eyssel mines in F rance yield an asphalt from bituminous
l i meston e extensively used for paving purposes A t S e yssel
there are seven beds of bituminous limestone varying from 10 fe e t
to 2 0 feet in thickness and containing from 4 to 10 per c ent of
bitumen
The Tu rkish supply is mainly derived from Albania and
Pales t ine The depos i ts in th e D ead S e a region hav e long b e en
notable The bitumen springs at N ebi M usa contain from 30 to
4 0 per cent of asphaltum
The ozokerite deposits at Boryslaw in G alici a Austria supply
p ra c ti cally the world s annual output
,
,
,
,
,
.
,
,
,
,
,
.
,
,
.
.
.
-
.
.
.
,
,
,
’
.
B ARY T E S
.
This mineral is found as irregular masses in schists and l l me
s tone
I t is often associated wi t h lead ores
The world s production is pr i ncipally obtained from G ermany
G reat Brita i n U n ited States and B e lgium On e of the largest
-
.
.
’
,
,
1
2
Leon M al o L
F V G reene
,
.
p
.
.
3 5 5 , 1 888
.
,
P i
A sp h a lte, p 2 0 , ar
s h al
a n d its U
,
’
Ap
t
.
.
s,
s
e
18 88
s
T
ra n s A m I
,
.
.
.
n s t.
AL E
,
v ol
.
vii
x
.
A N D MIN ER ALS CO N S I D ERE D E CO N O M IC A LLY
0 3 11s
14 7
.
known deposits occu rs at Silver I sland near the no rt h end of
Lake Supe rior
Baryt e s is now largely employ e d i n t h e manufactur e of paints
Th e price of th e raw ma ter i al varies from 1 2 3 to 2 18 per t on
,
.
.
.
B AU " I T E
S
e
e
(
.
Alu m
“
B I S MU T H
.
.
.
.
M etall i c b i smuth g e n e rally occu rs in v e ins in gne i ss schist and
clay sla t e accompany i ng or e s of silver cobal t lead wolfram z i nc
and gold It i s c h ie fly derived from t h e s i lv e r and cobal t m i nes
in Saxony a n d Boh e mia
The p rinc i pal ores of commercial value are th e sulphi de
telluri d e and carbonate which ar e found ass ociated wi t h m oly b
de n ite fl u o rite pyr ite s chalcopyr i te and apat it e
The worl d s supply of bismu t h comes pri ncipally from the S ta te
mines in Saxony Small quan titi es come from Colo rad o Ne w
South Wal e s and Queensland
The supply i s greater than the demand and or e s conta in i ng le s s
than 5 per c e nt of the m e tal leave no margin of profi t Th e
price is abou t 68 pe r pound
,
,
-
,
,
,
,
,
.
.
,
,
,
,
,
,
,
.
’
,
.
,
.
,
.
.
.
.
B
O
RA"
.
This mineral occurs as i ncru s tations in old lak e bas ins i n rain
less r e gion s and mix e d w it h clay in mars hes and shallow lagoons
Col e manite which is a ca lcium bora te is found in Californ i a i n
bedde d depos its as larg e mass e s mor e or l e ss connected by
s t ring e rs a n d bands N ear D agg et t th e coleman i t e deposits vary
1
from 5 f e e t to 30 fe et in thickn e ss
The worl d s supply i s derived from t he Un ited S ta te s Chili
Peru I ta ly and Turk e y The produc t ion of th e United States
i s ch ie fl y deri v e d fr om th e col e mani te d e pos its in Californ i a
B owie a c id which i s largely u s e d in t he manufactur e of borax
is obta i ned from th e gas e ous e mana ti ons of steam fumarol es i n
vol c anic regions The ent ir e yi e ld of it from It aly is d erived from
the fuma rol e s in th e Provinces of Pisa and G ros seto
.
,
,
,
,
.
.
,
.
’
,
,
,
,
.
.
,
,
.
.
C EME
N
T
.
Ch e mically considered cement i s an int i ma te admixtur e of lim e
and clay Ther e ar e two kinds of cement in th e mark e t— namely
a rt ifi c ia l and natural
,
,
.
.
C am pbell Rec o nnai sa n e o f th Borax De p it o f D e th
”
M oj ave De ert B l let in f the U S G l S
2 00
y N
R
.
s
c
s
,
,
u
o
os
e
.
eo
.
u r ve
a
s
,
o
.
,
14 8
MININ G GEOLOGY
.
c e ments are made in almost all civilised c ountries
c e m e nts are produc e d direct from rock containing
more or less the requisite proport i ons of lim e an
United States and N e w Zealand produce c on s id
of natural c e ment from argillaceous limestone deposits of great
e xt e n t
Th e hydraul i c limestone at G renoble in F rance from which
the fin e s t natural cement in th e world is produced occurs
bed 15 feet thick interbedded i n a c ompact l i mestone I ts com
position is as follows
A r tifi c ia l
N a tu ra l
.
,
.
,
,
,
.
,
P
S i l i ca
Alum i na
I ron oxid e s
Calcium carbonate
M agn e s i um carbo n ate
Water loss etc
e r c en
t
.
to
,
,
,
,
,
,
.
traces
,
,
10 0 0 0
The hydraulic limestones in Ne w Z ealand are of Upp er
Cretac e ous age They vary from 2 0 f e et to 1 4 0 feet in thickness
Cement manufactured from the rock at M ahurangi show e d th e
follow i ng composition
.
.
S i lica
Alumina
I ron oxides
L im e carbona t e
M agnesia carbonate
Alkalies and loss
,
,
,
,
,
10 0 0 0
Th e iron seldom exceeds 3 per cent I t mostly o c c urs as
grains of glauconite
N a tu ra l c e ments ar e often e qual to the best a rtific ia l Portland
cements bu t g e nerally speaking t hey lack th e uniformi ty in
composi t ion of the a rtifi c ia l prod u ct
.
.
,
,
,
.
C H R O M I UM
.
Chromite of iron occu rs in irreg u lar masses in peridotite and
s e rp e nt i ne The world s supply is principally produced by
Turkey N ew Caledonia G ree c e Ne w South Wal e s Canada a n d
’
.
,
,
,
,
,
15 0
MININ G GEOLOGY
.
hydrous oxide of manganese mixed with a variable pe rcentage of
cobalt
The ores of cobalt are g e n e rally found accompanying those of
nickel and silver and som e tim e s t hose of copper and manganese
Th e cobaltif e rous bands at S ku tte ru d i n N orway cons i s t of
alt e rnating thin b e ds of m i ca schist and quartz schis t th e latt e r
impregnated with pyrites cobalt glan c e cobaltif e rous mispick e l and
a li t tl e chalcopyri t e S o far th ey hav e not proved of much va l ue
The hydrat e d oxid e of cobal t of N ew Caledonia is largely
expo r ted to E urope and America I t occu rs intimately associated
w ith hydrat e d oxide of manganese which is found in irregular
t
of
red
clay
in
serpentin
e
This
obaltif
e
rous
wad
contains
c
k
e
s
o
c
p
from 2 5 to 5 p e r ce n t of cobalt and at present is the principal
source of the world s supply
U p till th e end of 1 90 1 a consid e rable po rtion of the domestic
supply of the United States was obtained as a by product in the
treatment of the lead ores from M ine L a M o t te in the S tate of
M issouri
.
,
.
,
,
-
-
,
,
,
,
.
.
.
,
.
,
.
’
.
-
-
,
.
C O PP ER
.
The chief sou rc es of cop pe r are the sulphides — prin c ipally the
yellow sulphid e — and nativ e coppe r When t he ore occu rs in
large masses capable of being c heaply mi n e d 1 to 3 per cent of
th e metal is payable Th e great bulk of th e copper annually
placed in the market 1s produced from very low grade or e s
asso c iat e d with iron pyrites and often c ontaining a little gold and
silver
The most important copper mines of t he world at the presen t
t ime are those of M ansfeld in G e r many 5 Rio Tinto and Tharsis
in Spa i n 5 San D omingo in Portugal 5 L ake Superior M ontana
and Arizona in the United States 5 and M ount L yell in
Tasmania
The world s production of c opper amounts to over
tons
of which the Uni t ed S tates p r odu c es over 5 5 per cent
U N I T E D S T A T E s — A t L ake S uperior in M ichigan the copper is
found in beds of conglomerate and sandstone in t e rs tra tifie d with
fl o ws of amygdaloidal diabase forming what is known as th e
—
K e weenawan series and which is probably of pre Cambrian age
The c onglome rates are the most productive I n th e m the copp e r
occurs as the cementing material 5 it has evidently been deposit e d
from an aqueous solution The diabase fl o ws are amygdaloidal i n
their upper layers and o cc asionally the lower side also may be
1
vesicular
They contain ri c h patch e s of native copper associated
with native silver
1
T A R i c k ard T h e Copp er M ines of L a ke S up er ior p
N e w Y ork
.
.
,
.
-
,
,
.
-
,
,
,
,
,
,
,
.
’
,
.
,
.
,
,
,
.
,
.
.
,
.
.
.
.
,
,
.
.
0 11115
AN D MIN ERALS C O N S I D ER ED E C O N O MI CA LL Y
15 1
.
Copper i s also found in fis s ur e veins crossing th e Keweenawan
se ri es of th e nort hern end of th e peninsula Th e v e ins vary from
10 feet to 30 f eet in wi d t h
Th e y ar e riches t in th e diabas e
i n which t he copp e r occurs in the nativ e s tate being gen e rally
foun d in mass e s t he larg e s t mass w ei ghing nea rly 600 to ns
“
Th e mos t productiv e min e s i n t h i s reg i on are th e Calum et
” “
” “
”
”
“
and Hecla
O sceola
Tamarack and Quincy
The two
fo rmer have shaf ts r e ach i ng th e great d e pth of nearly 5 0 00
fee t
It sho uld b e noted tha t e xtr e m e ly low grade or e containing as
littl e as 1 5 p e r c e n t of coppe r ar e mad e to y ie ld large p rofi ts in
t h e Lak e Superior dist ric t To achiev e this resul t enormous
quanti t i e s of or e ar e min ed and stampe d
Th e d i stinguishing f e atur e s of the M ichigan copper mines are
t he e normous tonnag e of low g rade ore stamped t he low cos t of
produ c tion and th e gr eat depth of th e mines
The production of the copp e r min e s in Butte distric t i n
Montana is e v e n gr eate r than that of th e L ak e Superior m in
Th e mos t product i ve min e s a re the Anaconda Pa rr o t Bu t te and
Boston Boston and M on ta na and Colo rado
The copper is found in east and west lod e s in gr anite The
main lod e which runs t h rough t h e An a conda and Pa rrot mines
has proved p rod uc t ive for a dis tance of 3 m il e s alo n g the stri ke
Th e av e rage width of t h e lod e s is 10 feet T h e coppe r occ ur s
princ i pally as sul phides which ar e s ilv e r—bearing t he propo rt ion
of s ilver varying from 5 o z to 2 o z pe r un it of c opper
The Arizona copper m ines produce larg e quantities of oxides
and ca rbonates which occur in or n ear a Carbo nif e rous limesto ne
often nea r the poin t of contact with gr anite or with sandston e s
S P A I N AN D P O R T U G AL — Th e copp e r depos its a t Rio T i n to
Tharsis and San D omi n go ar e of great exte nt They con sist
of compa ct pyrit e s conta i n i ng from 1 to 2 5 per c en t of copper
pyrites d i ss e minated t hroughout t he whole mass
N ext to the Calum e t and H e cla t he Rio T i n to is t he greatest
c opp e r m in e in t he globe
G ER M AN Y — The M ansfe ld copper min e s i n S axony have b e e n
work e d sinc e the twelf t h centur y The or e is found in a fl a t
lying bed of cupriferous shal e of Upp e r P e rmi an ag e and not
withstand i ng its th i nn e ss and compara t iv e ly low g rade in metal
it can b e work e d wi th p rofi t It occurs in fi n e ly dis sem inated
pa rticles throughout t h e shal e A gold e n y e ll ow colour indicates
chalcopyr i tes ; a bl u ish a n d reddish va ri e gated colour in dicates
borni t e ; a ste e l —gray copper glanc e 5 a grayish yellow i ron
pyri tes ; and a l e ad e n gr ay gal e na
Th e whol e bed conta i ns c opper but o nl y th e botto m 3 inch or
-
.
,
.
,
,
.
,
,
,
.
.
-
,
,
.
.
-
-
,
,
.
-
,
,
,
,
,
,
.
.
,
,
.
.
,
,
.
.
.
-
,
,
,
.
-
.
,
.
,
»
.
.
,
-
.
-
.
.
,
,
,
.
-
.
-
-
,
,
-
.
,
,
15 2
MININ G
G
EOLOG Y
.
inch are rich and on an a ve rage contain 2 to 3 p e r c e nt of
copp e r and 16 3 oz of s ilver to the ton of copper
A U S T R ALA S I A — M ount L yell M ine on th e w e st coast of T a s
mania is on e of the principal copper produc e rs in th e Com mon
w e alth of Australia
A t t he surfa c e the lode was a huge gossan consist i ng of dense
dark h ae matite and friabl e limonite containi n g gold and silver
Below the oxidis e d zon e the ore pass e d into massive pyri te s l y ing
between talcos e sch i sts on on e side and conglom e rates on the other
I n N ew S outh Wal e s there is a copper bearing area variously
estimated at from 5 0 0 0 to 6 5 0 0 square mil e s I t is situate d in
the great arid plain lying b e tween the D arling Be gan and
L achlan rivers The c ount ry r oc k is Silu r ian slate whi ch is
trave rs e d by fi s su re veins N one of the mines have been work e d
continuously
4
.
,
.
.
,
.
-
,
.
,
.
.
-
.
°
,
,
-
,
.
-
.
.
C RY O L I T E
.
This is a fl u oride of sodium and aluminium containing
about 5 1 per cent of sodium fl u oride when pur e
Practically
the whole of the world s supply is obtained from the D anish
cryolite mines at I vigtut on th e west c oast of G reenland
Th e white cryolite o cc urs in great snow white masses which
ar e par t ially transparent I t constitutes a large bed or mass in
a granitic dyke which traverses a gray gneiss
Associa te d with the cryolite are quartz siderite gal e na pyrit e s
chalcopyrite wolframite ; also fl u orite mispickel and cassiterite
The ore is c on fin e d to the granite but there is no clear lin e of
demarcation between i t and the surrounding roc k into which it
pas ses The mineral is mined by ope n cuts about 2 0 0 feet wide
1
and 10 0 feet or more d e e p
T h e G reenland mines pr oduce nearly 8 0 0 0 tons of c ryolit e a
year valued at about £ 3 per ton at the mines Th e bulk of t h e
output is exported to the U nited States for the manufactur e of
alumini u m for making sodium and aluminium sal ts and for the
manufacture of s odium fl u oride which is used to prev e nt incrusta
t i ons forming in steam boilers
Cryolite is also used to a limited e xtent in the man ufacture of
an opalescent glass which resembles F r e nch porc e lain
,
.
.
’
-
.
,
-
,
.
.
,
,
,
,
,
,
.
,
,
.
.
,
.
,
,
,
-
.
.
D IA M O ND
.
Until the dis c overy of the mines at J a g e rs fon t e in and Kimberl ey
in the years 18 70 and 18 7 1 th e re is no record that diamonds h a d
been found exc e pt in alluvial deposits or conglomerates
1
M in er a l R e sou rces of U n ited S ta tes 1 90 1 Wash i n gt on p 883
,
,
.
,
,
,
.
.
15 4
MININ G GEOLOGY
.
blue or dark green colour in pla c es resembling some va r ieties of
serpentine
F our fifth s of the material forming the blue gr o und is a dark
green dense serp e n t in e which c ontains glistening plates of brown
mica small dark red garn ets ( mostly pyrope ) larg e dark green
crystals and grains of olivine b e sides enstatite smaragdit e
ch rome diopside ch romite magnetite and ilmenite Small frag
ments of al t ered black shale are often so abundant as to giv e t he
rock a b r ec c iated appearance
-
,
.
-
,
-
-
,
,
-
,
,
,
,
,
.
,
.
FI G
a,
e o gro und
f Q artzite
Y ll w
ph y re
.
67
.
,
—S e c tion o f Ki mberley D iamond
a ct ,
.
u
.
.
g,
B lue gro u
S late s
nd
.
5,
Ba l t heet
sa
s
.
Pipe
a,
.
S h a le s
.
d , M ela
.
The blu e g round is g reasy to the touch When e xposed to
the weather for a time it soon disintegrates and is then eas i ly
crush e d th e diamonds being afterwards extracted by washing and
hand —pick i ng
1
Th e late Prof e ssor H G L e wis described the blue ground as a
porphyritic vol canic peridotite of basaltic stru c ture for which he
”
proposed the name Kimberlit e
I t has be e n not e d by several write rs that while the c o mposition
of th e m aterial fillin g the pip e s appears to be th e same in all e ach
mine has its own parti c ular kind of diamond which is so distinctive
1
Pro fess or H 0 L ewi s T h e Matri x o f th e D iam ond Manch ester
M eeti ng B riti sh A ss oc iation A u g a nd S ept 1 8 87
.
,
,
.
.
.
.
,
“
.
,
.
,
,
,
.
.
.
A N D MIN ERAL S C O N S I D ER ED E C O N O MI C A LLY
oa a s
155
.
tha t an exper t buyer can usually say from which mine any
pa rticular s tone is derived
A ce r tain propo rtion of the diamonds are broken crysta ls and
or p e rhaps n e ver hav e th e corr e sponding p i ec e s b ee n
s e ldom
.
,
,
,
M any of the diamonds ar e in a state of str e ss and som e fl y t o
pieces or splinte r wh e n re moved from t h ei r ma t rix and wh e n
,
being cut
1
Professor Bonney b e li e v e s that the d i amond is a primary
cons t itu e nt of t h e i gn e ous rock as much as th e garn et m i ca and
oth e r minerals with which it is assoc iated He believ e s tha t th e
diamond was forme d nei t her by th e a ct i on of molte n rock on
carbonaceous ma t ter nor by th e action of ste am or ho t wa ter in
a subsequent solfata ric stage of t he vol ca no but w as se g re g ra te d
by the usual proc ess e s of di ff erentiation in so me d e eps e ated
magma which was afterwa rds forced up from b e low into the
.
,
,
.
,
,
p
s
1
.
Williams agrees with Profess or Bonney that the
blue gr ound must b e d e signated a breccia w hi ch h as been
forc ed up from b e low by som e igneous ag e ncy poss ibly in th e
nature of a mud volcano Among the fac t s which led h i m to
thi s belief h e mentions the fr e quent oc c u rrenc e of b r oken diamonds
e mb e dded in th e hard Kimb e rlite as well as pebbl e s and boulders
with po lished surfaces as if wat e r wo rn
Professor L ewis advan ce d the theory that t he diam on ds were
formed from hydrocarbons de rived from t he fra g ments of
carbon a ceous shale enclos ed in the blue gr ound which he
r e garded as a true lava
This view is contested by M r
Williams who sta tes that all the pipes co nta ining Kimberlite
do no t conta in diamonds while diamonds exist in som e mines
such as t hos e in the Pr e toria district wher e no carbonac eous
shal e s are to be foun d
—
M r Williams while agreeing
P ar e nt R o c k o f D ia m o n d
with Profess or Bonney that th e diamonds ar e a primary con
—
t
i
t
u
n
t
of some deep seated ign eo us r ock d e ni e s that e clog i te
s
e
i s the parent roc k of t he g em s at Kimberley
3
Profe ssor Bonney in 1 8 99 r e ported the discove ry of diamonds
in sp e c i mens of a coa rsely crysta ll ine garnetiferous roc k rela t ed t o
eclogite obta ined from the N e wla n ds min es situated about 4 0
miles fr om Kimb e rley
Commenting on th i s discove ry h e
F
,
.
,
-
.
,
.
,
,
,
,
.
,
.
,
.
,
,
,
,
,
.
1
p
Pro fe or
ss
.
.
G
.
B
onney
,
P
r oceed in gs
th e R oy a l
f
o
S ociety ,
Will iam T h G ene i o f th D iamond T
p et S ept 190 4
M E P
Pro fe or Bonney P r ed i g f th R y l S oci ty vol l x v
3
G
ardn er
T
,
,
3
F
am h l
ss
s,
.
,
.
,
“
e
s s
e
ra n s .
,
v ol .
A m I
.
lxv
.
ns t.
.
oce
n s o
e
o a
e
,
.
.
p 2 2 5 , 1 8 99
.
.
15 6
MININ G GEOLOGY
c on c lu de d
.
e clogite was the pa re nt rock of
dia m ond in
S ou th Africa a view which has generally been acc e pt e d by
E nglish geologists since that date
The s tatem e nt that eclogit e was th e or i ginal ma t rix of the
diamond caused M r Williams for many y e ars G e n e ra l M a n a g e r of
th e Kimb e rley min e s to carefully exam i n e th e eclogit e wh i ch
occurs in tons in all the pip e s w h e re i t is tr e at e d as waste rock
T w e nty tons of this rock wer e coll e ct e d and tested by crush i ng
and j igging in a test plant but not a single diamond was found
in th e material
M r Williams further states that h e had also
examined hundr e ds of pi e ces of e clogit e but nev e r found a
diamond nor had he ever h e ard of a diamo n d having been
found in this rock during all th e y e ars the min e s had been
worked
The occurren c e of diamonds in the eclogi t e from N e wla n ds M ine
must be regarded as sporadic and not general That a peridoti t e
or some ultra basi c igneous rock was the parent—
rock of S outh
African diamonds may be inferred from the laws of magmatic
parage n esis
G e n e s is o f D ia m o nd — Assuming the diamond to be a primary
constituent of an igneous ro c k the original condition of the
carbon is still a matter for conj e c tur e D id t he gem crys t allise
from carbonaceous matter from a hydrocarbon carbon dioxide
or a carbide ? Oi the source of the carbon nothing de fin ite is
known or of the proc e sses which prevented its oxidation along
w i th the iron with which it is always associated I t is important
to remember that th e diamond bea ring pip e s in the Transvaal
penetrate carbona c eous shales
Williams mentions that large diamonds have been found en clos
ing small ones while twins a re not rar e from which it may be
inf e rred that th e formatio n or growth of the diamond follow e d
the ord i nary laws of c rystallisation in a magmatic solution of rock
mat e rial
M oissan in his diamond—making experiments fused 1ron I l Ch in
carbon and allowed it to cool in such a way tha t the separation
of the e xcess of carbon took place under pressure I n t his way
micros c opic diamonds were formed M ic ros c oP ic diamonds hav e
been found in ordinary cast iron 5 hen c e it is inferr e d that
abno rmal pressure is not ne c essary to ensure success in the
exp e rim e nt
The exp e riments of D r F riedlander have a close r bearing upon
the natural formation of d i amonds Fr ie dla n de r l fused a small
pie c e of olivine a c e ntimetre in diamet e r by m e ans of a gas blow
1
E F He n e ag e
T h e P h en omen a o f th e D i a m o n di fero us D epo s its in S ou th
A fri ca T r a ns I n st M in a nd M et v ol xii p 1 2 5
th a t
-
‘
th e
,
.
,
.
,
,
.
-
,
.
,
,
.
.
-
.
.
,
.
,
,
,
,
.
-
.
,
,
.
‘
,
,
,
.
.
-
.
.
,
,
.
.
,
,
.
.
.
.
.
.
.
15 8
MININ G GEOLOGY
.
ravines to the c onglomerate beds which provided the material
c ontained in them
The conglomerates are c h ic fl y composed of a
micaceous sandstone which is manifestly not the original matrix
of the diamonds The gems wer e pro bably d e rived from some
rock surface subj e c ted to denudation a t the time the sandston e
was being formed
The greatest diamonds of whi c h there is any re c ord prior to
1 90 5 are the Koh —i nor 7 93 c arats the G reat M ogu l 7 8 7 5 c arats
and the Regent 4 10 carats all found in the great mines of G an i
A ston e of over 4 0 0 carats
Cou l ou r and G ani P a r te a l in I ndia
was found at Kimberley in 18 8 4 and one of 97 2 carats named
”
“
the E xcelsior at Jagersfontein The great Cullinan diamond
found e arly in 1 90 5 in the Prem i er M ine 3 1 miles from Pretoria
is r e ported to weigh
carats its size being 2 5 inches by 2
inch e s by 4 inches Th i s is th e larges t stone i n the world I t
is said to b e p e rfe c t l n c olour and free from fl a ws
The great bulk of t h e world s supply of diamonds at present
comes from the Kimberley m i nes wh i ch in 1903 are reported to
have produced stones to the value of nearly four millions sterli n g
.
.
-
.
-
,
,
,
,
,
,
-
,
.
,
,
,
.
,
,
,
.
.
.
’
,
.
FI RE C L A Y
.
This material occurs in s tra tifi e d laye rs or beds generally in
associat i on with seams of coal As a rule it lies u n d e 1 the coal
and is the soil on which the c oal vegetation grew
F ire clays are found in all c oal bearing regions but all coal seams
are not u n derlain by material suitable for use as a fi r e clay G ood
fi r eclay s should contain from 5 2 to 62 per cent of silica 2 2 to 3 2
per cent of alumina and 10 to 14 p e r cent of wate r The presenc e
of 1 per cent of lime magnesia potash or soda renders a clay
too fusibl e to be u seful for fi r e c lay pu rposes I ron oxides ar e
also inj urious and when over 3 per cent of the protoxide is
present the clay should be dis c arded S tou rbridge fi re c lay con
tains about 2 per cent
—
China clay or kaolin is found in veins and irre g ular deposits in
places where granite has b een altered probably by the emanation
of steam and gases from c racks and fi ssu r e s
I nvestigation has shown that the kaolinisation of granite a n d
other highly acidic rocks is not the result of mere atmospheric
weathering That decomposition of th e f e lspa rs in the zon e of
katamorphism does take pla c e is well known but the deep seated
kaolinisation which h as been noted in Corn wall D evon N ew
S outh Wales Qu e ensland and N ew Zealand must be ascrib e d to
fumaroli c age n cies
,
.
.
-
-
,
.
,
.
,
.
.
.
.
,
,
,
.
,
.
.
.
.
.
-
,
,
,
,
.
,
O RES
MIN ERAL S C O N S I D ERED E C O N O M I C A LLY
AN D
FLU O R I T E
.
1 59
.
fl u ors p a r
This mineral ofte n called
is generally found i n
veins in limestone gneiss sandstones and c lay sla t e I t also
occur s as the gangue of meta lli c ores especially of lead
F luorite is c hie fly used as a fl u x for iron -ores A small quan tity
is employed in the ma n u fa c tu 1 e of opalescen t glass and for th e
produ c tion of h y d1 ofl u or ic ac i d
The world s output amoun t s to over
tons a y e ar of
wh i ch th e Un i ted Sta tes produces about one t h i rd and Pru ssia
abou t on e quart er Th e value varies from 1 68 t o £ 1 2 s p e r ton
“
,
,
-
,
,
,
.
,
.
.
,
.
’
,
-
-
.
,
.
G
O LD
.
.
.
This m e tal is found in v e ins in nearly all kinds of rock wi thou t
r e ga rd to ag e compos i tion or si t ua ti on The most produ c t iv e
v ei ns ar e thos e t rave rsing Pal aeozoic s e dimentar i es anc ie n t
granites and older Tertiary e ruptives especially thos e of a s e m i
bas i c type
Th e d e nudation of gold b e aring rocks has libe rated large
quantiti e s of gold which ha ve become more or less conc e n tra t ed
in alluv i al gravels or place rs These plac e rs ar e foun d of all ages
exten ding from M iddl e Te rtiary to recent t imes
Th e gold found in veins traversing rocks of Pal aeozoic or older
Secondary age i s g e n e rally of high valu e wh i le tha t derived from
veins in andes ite and o t her old e r Tertiary e ruptives is commonly
of low valu e being largely alloyed with s i lv e r
The gold of Aus tral i a mainly or en t irely der i ved from roc ks of
Pal ae ozo i c ag e is of h i gh value 5 as also is tha t of t h e Transv aa l
The gold found in t he Pal aeozo i c mica schis t s and sla te s in t he
South I sland of Ne w Zealand i s al mos t pur e 5 while tha t deriv e d
from the Te rtiary andesi t es in Aucklan d i s of low value being
alloyed wi th on e third in w e ight of silv e r
Th e same f eature characterises t he gold produc ed in t he
N or t he rn H e mispher e Russian gold is of high value wh i le that
derived from the andesi tes of Transylvania is of low valu e
Th e vein and pla c er gold of Cal i fornia is commonly v e ry pure 5
but that of Ne vada and Colorado mos tly deri v e d from veins
trav e rs i ng later e r uptives is of low grad e being gen e rally alloyed
wi t h a larg e propor ti on of silver
This p e cul i ar phenomenon is too general to b e accidental I t i s
a happ e n i ng of wh i ch no adequat e e xplanation can at presen t b e
off e r e d
A cons i derabl e quantity of gold i s d e rived from s i lver copp e r
,
.
,
,
,
,
,
.
-
,
.
,
.
,
.
,
,
.
,
-
,
-
.
.
,
.
,
,
,
.
.
.
,
,
16 0
MININ G GEOLOGY
.
and lead ores 5 and a smaller amo u nt from ores of antimony
ars e nic manganes e a n d tungsten
The value of the world s production of gold for 1 90 4 was
e stimated at £7
The gold produced by t he fi v e gr eat producing r egions i n 1904
and 190 5 according to M r F Hobart wa s as follows
,
,
,
.
’
°
,
,
.
1 90 4
Transvaal
U n it e d Stat e s
Australasia
Russia
Can ada
.
,
,
,
,
,
Th e most productive g oldfi e ld centres in the globe are the Rand
Kalgoorli e and Cr i pple Cr e ek
I n the Commonwealth of Australia and United S tates which
are of continental d i m e ns i ons the gold bearing d e posits o cc ur
under many vary i ng geological condition s
—
V I C T O R I A I n th i s State the gold is derived from thre e principal
sources— namely from quartz veins from Tertiary deep —leads and
from recent gravel drifts
The de e p leads consist of placer gravels of M ioc en e and Pliocene
age The latt e r hav e prov e d th e most prod u ctive and are in many
places as for example near Ballara t protected by a thick sheet
of basalt the lava having fl o we d down the ancient valley and
cov e red up th e river gravels and sands
The quartz veins occur mainly in Silurian slates The gold
bearing veins at Bend i go belong to the interesting class of or e
d e posits termed sa ddle reefs wh i ch occur in the crown of a n t i cl i nal
arches and send down tapering prolongations or legs r u nn i ng
more or l e ss parallel with b e dding plan es of the country rock
The distin c t i ve feature of the veins in t h e Ballarat G oldfie ld is
the presence of the famous indica tor beds These are thin beds
of black carbonaceou s pyritic slate which occur in th e Silurian
slates and consequently constitute a dis t inct member or horizon
of the country rock T h e slates stand in a nearly v e rtical
position wh i le th e contained gold bearing ve i ns l i e nearly hori
z on ta l
Along the plane of intersect i on of the quartz veins and
indic a tors ther e g e nerally occu rs ri c h ore
W E ST ER N A U S T RA L I A — Tu this State the c rystall i ne schists
which form the base m ent rocks of th e country are trav e rs ed by
wide belts of ancient eru ptives These eru pt i ves are dioritic or
hornblendic in different pla c es and are often so much altere d th a t
the i r original c h aracter i s not always easily det e rm i ned : A t
Kalgoorli e th e hornblendic belts have been altered and s ilic ifie d
,
.
,
,
-
,
.
.
-
,
,
,
.
-
,
.
,
,
,
,
,
.
-
.
-
,
°
,
,
-
-
.
.
,
,
-
.
-
,
-
.
.
.
.
,
,
1 62
MININ G GEOLOGY
.
Silurian age 111 the L isle and G ol c onda G oldfie lds gold occurs
in veins intersecting a belt of granite
N E W Z E ALAN D —I n this colony gold is found in r e cent and
Tertiary place rs and in quartz v ei ns I n O tago the gold bearing
veins o cc ur in Silurian mi c a schist 5 in Reefton distr i ct in clay
stones and sandstones of suppos e d Carboniferous age 5 and in t he
Hauraki Peninsula in altered andesites of M iddle T e rtiary age
Th e quartz conglomerates and cements at the bas e of th e
M iddl e Tertiary coal measures contain wat e r wo rn gold but
seldom in payabl e quantities It is noteworthy how e ver that
many of the richest pla c ers in O tago and Westland are a rewash
of these ancient grav e ls
U N I T ED S T AT E S — The gold of th i s country is obtained from
veins or from plac e rs resul t ing from the e ros i on of gold bearing
country and th e concentrat i on of the valuabl e contents
I n the State of Cal i for n i a the vein system known as th e
”
M other L ode is contain e d i n slates a n d al t ered ign e ous rocks
of Carbonif e rous and J u rass ic age I n Tuol u mne and Calav e ras
1
counties and more particularly at N evada City and G rass V alley
the v ei ns o c cur in a n d near intrusiv e masses of granod i orite Th e
placers along t his gold belt are among the richest in N or th
America Th e age of this remarkabl e stretch of gold bearing
veins i s believed to be Cretaceous The contained gold is of
high quality
A second gold belt of great importance li e s in E astern Cali
f o r n ia w i thin the watersh e d of th e Colorado River
111 this b e l t
the v e ins o c cur in andes i tes phonol i t e s and trachyte of probably
Mi ddl e Tertiary age The gold is alloy e d wi th s i lver and assoc i
ated with silve r or e s pyri te s et c
Th e larger part of t he gold produ c tion of California is obtained
from the Cr e taceous b e lt
The gold produced in the State of Colora do is mainly deriv e d
from ve i ns trav e rsing Archaean granit e or the overlying andesitic
tu fts and breccias wh i ch are typically develope d in the Crippl e
Creek district These i gneous rocks wh i ch cons i st of h e avy fl o ws
as well as fragm e ntary mat t er are beli e ved by American g eolo
g i sts to be of post M iocene age
A cons i derabl e quantity of gold is also derived as a b y product
from the s i lv e r lead or e s of L eadville and other m i ning centr e s
wh i ch occur in v e ins in alter e d sed i m e ntari e s and e ruptives of
M esozo i c age Colorado is th e larg e s t gol d produc i ng Stat e i n
Am e rica The placer d e posits are not of gr e a t extent
The bulk of the gold of M ontana is derived from l e ad silv e r
1
Waldemar L i n”dgren T h e G e ol ogical Featu res o f th e G old Produ ctio n
o f N orth A m e rl ca T r a ns A m I nst M in E n g v ol xxxiii p 81 7
.
.
.
-
-
,
.
-
,
.
,
-
-
,
,
,
.
.
.
-
,
.
-
,
.
,
,
.
-
.
.
.
,
.
,
,
.
,
-
,
.
,
-
.
,
,
.
,
,
-
.
-
-
,
-
.
-
.
.
-
,
.
,
.
.
.
.
.
,
.
.
.
,
A N D MIN ERALS C O N S ID ERED E C O N O M IC A LLY
oat s
1 63
.
v e ins in Arch aea n rocks or from v ei ns of c opper or e occurring in
intrusiv e gr an i t e s of suppos ed Uppe r Cretaceous or L ow e r T e rt i ary
age princ i pally d e v e lope d near Butte
I n th e Sta t e of N evada the basem e nt rocks are sedimenta ri e s
of Pal aeozoic a n d Me sozoic ag e i n t rude d by many dyk e s of por
es
and
smothered
by
T
e
r
ti
ary
rhyoli
t
andes
i
t
e
s
and
h
r
p y y
basal t s Th e Comstoc k L od e long cel e bra t ed for its dry gol d
silver ores is con tain ed in a nd e si te The silver l e ad ore s of
1
E ur e ka occur in lim e s tones near e rup t ives a n d carry on e t h i rd
of th e ir value i n gold Th e gold s i lv e r m i ne D e Lamar i n
Sou th e rn Ne vada occurs in Pal aeozo i c quart z ite s
Th e gold bea ring deposi t s of Black H i lls in South D akota
b e long to two groups I n on e group t h e mos t i mportan t t her e
ar e t he mas s i v e lod e s of t he Homestake d i strict wh i ch cons i s t of
a bel t of Arch aean sch i sts clo s e ly in te rs ected in gr e a t ar e as by
th i n s t rings a n d v e ins of quar t z carry i ng free gold a n d gold
b e aring pyr ite s Th i s d e pos i t locally known as T h e B e l t is 6 0 0 0
3
f eet long and 2 000 f eet w i de
The or e is very low g ra de a n d i s
only rend e r e d p r o fi ta ble by t he magn it ud e of t h e O pera ti ons
Th e gold ou tput of Br iti sh Columb i a i s d e r i ved from placers
and v ei ns inte rsecting old e r M esozo i c and Pal ae ozo i c rocks I n
the Kootenay d i s t rict t h e gold occurs principa lly i n copper b e ar
ing v ei ns wh i ch inters e ct rocks of L ower Me so z oic ag e
A LAS KA — Th e gol d of th e c e l e brate d Treadw e ll Mi n e s on
D ouglas I s lan d in Alaska is d e ri v e d from a m i neral i s ed alb ite
d i or ite wh i ch accord i ng to Professor Beck e r has be e n al te r e d
a n d s ilic ifi e d by solfataric or hydro t h e rmal ac ti on
Th e d i ori te
occurs as i n t rusiv e dykes in black s la te s th e b e d d ing planes of
wh i ch th e y clos e ly follow
3
A C Spenc e r
s ta te s that th e or e b e ari ng dyk e s b e long t o a
seri e s of i n t rus i ons wh i ch app e ar i n te rrup te dly along th e s t r i ke
for a di s tanc e of about 3 m i l e s i n a zon e approximat e ly 30 0 0 fe et
w i de I n t h e gr e a te r par t of t h e i n t rude d area e xposur e s ar e
few a n d only small dykes outc rop on t h e s id e towa rd t h e centr e
of t he islan d 0 11 t h i s s i d e the zon e s e ems t o b e irr e gularly
l i mi t ed but nex t to t h e shore of G atineau chann e l th e bo rde r i s
de fi n e d by a h e avy b e d of gr ee ns t on e runn i ng parall e l w it h t h e
sla te s a n d th e in t rusiv e dyk e s and d i pp i ng w it h them toward
t h e adjac e n t chann e l Th e m i n e ral i sed dyk e s wh i ch cons tit u te
t h e known minable ore occur j u s t b e nea t h this gr e ens tone wh i ch
-
,
.
,
,
,
,
,
,
,
.
-
.
,
-
,
-
.
,
.
,
-
,
,
,
.
,
,
,
,
.
,
,
.
.
.
-
.
,
,
.
,
,
,
,
,
.
-
,
.
°
-
.
°
.
,
.
,
.
,
,
.
,
1
3
L i n dgren
F
B
T r a ns A
3
A C
l e t, A m
.
.
.
.
”
.
82 9
Fe a tu r es , e tc ,
“
r, T h e O re D s s f th e B lac
ar
n
l x v p 5 7 0 , 1 88 9
m I nst 111311 E ng ,
s
l y f th e T r a dw ll r D
S e n c r,
G
I ns t .11 E , p 14 , 1 90 4
,
G
eol og ic a l
C pe te
.
.
.
p
e
.
.
1
.
.
.
vo
eo og o
.
.
.
.
.
epo it o
k Hi ll f Dakota
ii
e e O e epo it A la ka P m ph
.
.
s
o
,
.
s,
s
,
a
1 64
MININ G GEOLOGY
.
thus c onstitutes the hanging wall both of the intrusion zone and
of the ore bodies M any of the dykes of a lb ite d iorite away from
the hanging wall have been greatly altered and impr e gnated with
pyrite but workable ore bodies have no t yet be e n discovered
i n them
T h e r e lat i ons of th e mineralised diorite dykes to the asso c iated
country rock are shown in th e accompanying diagram
-
-
.
-
-
,
.
-
.
C ro
Fig 6 8 —
.
.
e tio th ro gh A l k a T re dwell M i e
S i de o f D o gla I la d
( A fter S pe er )
n
ss - s c
u
u
s
as
n
s
-
n
a
nc
.
and
N
orth e rn
.
The gold is g e nerally associated with pyri te s in str i ngs of
1
quartz a n d calci t e ramifying t hrough th e or e body
The ore i s e xtr e m e ly low g rad e b u t notwithsta nding this the
annual pr ofi ts are large and r e gular
I n th e Yukon and N om e di stric ts th e gold is deriv e d from
placers
T R AN SV AAL Pract i cally th e whol e of the gold of this Sta t e is
d e riv e d from b e ds of pyr i tic quar t zose conglom e rat e int e rbedd e d
w i th quartzi te s of L ow e r Pal aeozo i c ag e Th e ba n ke t re e fs as
thes e gold b e ar i n g conglomerates are locally t e rm e d vary from a
Th e y d i p south at angl e s w hi ch
f e w i nches to 4 fe e t in thickn e ss
The most productiv e
a r e st e eper at the outcrop than e lse where
beds occur in a b e lt of quartzite about 1 1 5 feet thick
T h e gold i s not contain e d in th e quartz p e bbl e s bu t in th e
siliceous cement i ng matrix Th e bankets a r e r e markabl e for th ei r
great extent a n d un i form value over wide str e tch e s A deta i l e d
description of th e chi e f ba n k e t beds is given in Chap t er I I
R U SS I A — Almost all th e gold produc e d in Russ i a is d e rive d
from plac e r d e posits on the western fl a n ks of th e Ural M oun t ains
Th e footh i lls on th e west e rn slop e s of the range cons i st of younger
Pal aeozoic sedim e ntar ie s intruded by mass e s of granite dior i t e
and diabase G old bearing veins but not generally v e ry pro
-
.
,
,
,
.
.
-
.
,
.
,
-
,
.
.
.
,
.
.
-
.
.
-
.
,
,
-
,
.
1
P
R A
am h l
.
.
p et
Ki zie
,
e
e
o p o
i e D o gla I land A l k
xxx i v p 334 1 894
T h e T r adw l l G r u
fMn
p 9, T r a n s A m I n st M in E ng , v ol
n
.
,
.
.
.
.
.
s,
.
u
.
s
.
s
as
,
,
.
a,
”
,
1 66
MI
NIN G GEOLOGY
.
the presen t tim e F ranc e produces mor e than half th e
world s output Then follow the Unit e d Sta te s with an output
amounting to 30 p e r c e nt Canada with 8 p e r cent and G reat
1
Brita i n wi t h 7 p e r c e nt of th e total product i on
Gypsum is used in th e manufacture of plaster of Paris of
plast e r for interior walls of hous e s and for agricultural purposes
The price vari e s according to locali ty from 6s to 1 2 s per ton
At
’
,
.
.
,
,
.
.
.
,
.
,
.
,
,
.
.
Th e ores of iron of commercial valu e are sid e rite limonite or
brown h ae matite magn e t i te and h aematite or specular iron
The carbonat e or spathic ores commonly occur in beds forming
members of a s tra tifi e d s e ri e s or in lay e rs of nodular masses more
e specially in as sociation wi th coal measures Clay ironston e an
impure arg i llac e ous carbonat e of iron is common in most of th e
British c oa lfie lds and in thos e of P e nnsylvania and O hio in the
Uni te d S tates I n S cotland i t contains a large proportion of
carbonaceous matter and is known as bla ck—ba nd or e
The clos e association of coal and iron or e e nabl e d Britain for
many years to occupy a dominant position in the manufactur e of
iron and ste e l
Beds nodular layers a nd even veins of sp a thic iron occur in
many g e ological formations The v e ins are g e n e rally small and
of littl e value Among th e most valuabl e deposits of spathos e
ore outsid e th e Carboni fe rous coal measures ar e those of Cleve
land wh i ch occur in th e Mi ddle L ias of E ngland
The red and brown h ae matite deposits of B i lb oa in Spain are
of gr e at ext e nt and furnish about 7 0 p e r cent of th e raw ore
import e d into G rea t Britain for the manufacture of iron and st e el
They occur in bed s in a limes ton e of Cretaceous ag e
The brown h aematite deposits of the Unit e d Sta t es a r e of great
e xtent and valu e They e mbrac e all the vari e ties of hydrat e d
s e squioxid e of iron recognis e d as limoni t e g o thit e turgite bog
or e s e tc T h e principal produc e rs ar e the Stat e s of V irginia
W e st V irgin i a Alabam a Colorado and Pennsylvania
The H u ron i an and L aurentian rocks of N orth Am e rica c ontain
vast d e posits of magnetite and red h ae ma t ite which occur as hug e
contact deposits and as r e gional metamorphic masses in te rs t ra tifie d
with th e crystalline rocks with which they are associated
The most valuable depos i ts of magn e t i c or e occur in L aurentian
rocks in the S tates of Pennsyl vania N ew J e rse y N ew Y ork and
3
M ichigan
1
T h e M in er a l R esou r ces of th e U n i ted S ta tes Wash i n gto n 1 90 1
44
T h e M in e ra l R sou r ces of th e U n ited S ta tes 1 90 3 Was h i n gto n
,
,
,
.
,
,
,
-
.
,
,
,
,
.
,
.
-
.
,
,
.
.
-
,
,
.
,
’
,
,
,
.
.
.
.
'
'
,
,
,
,
,
.
,
,
,
.
,
-
.
,
,
,
.
,
,
3
e
,
,
.
,
.
A N D MIN ERALS C O N S I D ERED E C O N O M IC A LLY
0 112 s
1 67
.
Red h aemat i t e const i tu te s 8 3 per cen t of t he annual output of
iron or e i n t h e Uni te d S tates a n d con t inues to b e suppl i ed by t h e
L ak e Sup e r i or r e g i on Th e principal sourc e s of supply ar e t he
Me sabi Ra ng e in Mi nnesota w it h an annual o u tp u t of
tons 5 th e M enomine e Rang e in th e S ta tes of M ich i gan and
Wis c onsin with an ou tput of
to ns ; M arqu e t te Ra ng e
i n Mi chigan
to ns ; and G og e bic Rang e
tons
The annual output of the M esabi Ra ng e ha s n e v e r be e n
reached by any oth e r iron oré region in th e world the cl oses t
compe titor being th e Bil b oa district i n Biscayan Spain which
produces
tons
The ou tput of iron ore in G r e at Brita in amounts to nea rly
tons being ma in ly spa thic and haematite ores
The magne t i t e and sp e cular iron ore d e posi ts of S c andinavia
more espe cially of Sw e d e n ar e of g r e at e x te nt Th e y occur
g e nerally in crys t alline rocks in som e districts as r e gional
m e ta morphic d e posits and in o t h e rs as c on ta c t d e po s its g e n eti cally
co n necte d with eruptiv e s The to tal annual o u tput is about
tons the bulk of which i s e xpo r ted t o G ermany
I ron o r e s of comm e rcial valu e are not very abundan t in
Australasia What h as b e en d e scribe d as t h e mos t importa nt is
tha t at th e I ron Knob and I ron M onarch 4 1 m i l e s W S VV of
Port Augus ta i n Sou t h Australia which has been es ti ma t ed to
1
conta i n
tons of h i gh grad e h aema tit e and mangan i c i ron
111 N ew Z e alan d a large d e pos i t of l i mon ite oc cu rs a t Pa rapara 5 and
e normous quan t it ie s of ti ta nic iro n sa n d ar e d i s tributed along th e
s hor e s of Taranaki and Patea
I ron or e s con ta i ning l e ss than 4 0 per cent of the metal ar e
rarely smelt e d and only t hos e conta i ning over 50 p e r c e nt ar e
consid e r e d rich
A rich commercial sampl e of r e d h ae ma t i te
should con tain from 60 to 6 5 pe r c e nt of t h e m e tal
A d e posi t of i ron to b e com e of any marke t valu e mu s t b e of
gr e a t e xt e nt mus t con tain rich or e be fr ee from s i l i ca sulphur
and phosphorus e as i ly smelted s i tuated in th e proxim ity of coal
and limeston e or so acc e ss i bl e to d ee p wat e r t ha t i t could b e
transpo rt e d to t h e sm e l t ers a t a min imum cost for handl i ng and
w i t hin e asy reach of t h e grea t mark e ts of t h e world
Sil i ca i s t h e most d e l e t e rious matt e r found i n iron ores and
should not e xce e d 1 0 per c e n t Sulphide—or e s ar e of no com
m e r c ia l valu e for t he produc t ion of i ron as the whole of t he
sulphur can only be r e moved by a dead oxi di sing roas t wh i ch is
a cos tly op e ration I ron pyri t es howev e r i s m i n e d for the manu
facture of sulph u ric acid D e posits of rich h aema ti te are some
1
N ote s on th e Iro n a n d P ho s ph ate D epo s its o f S o u th
H Y L B ro w n
A u stralia S u pp le me nta ry M in i ng R ecords 1 90 5 p 6 A dela i de
.
-
,
.
,
,
,
,
,
,
,
.
-
,
,
,
.
-
.
,
-
,
,
.
,
,
.
,
.
.
.
,
,
.
.
,
-
.
,
.
-
.
.
,
.
.
,
.
,
,
,
,
,
,
,
.
-
,
.
,
,
-
,
.
,
.
.
.
,
.
,
,
,
.
.
.
1 68
MININ G GEOLOGY
.
times rendered val u eless by the presence of a percentage of
sulphid e or e
Arsenical pyrites is generally of 11 0 value as a source of arsenic
e xc e p t it conta i ns gold or tin
The pr e sence of sulphur c opper or arseni c in iron or e s should
i n no case exc e ed
per cent The cok e availabl e for smelting
must not conta i n sulphur exce e ding 1 per cent
I ron ores for the manufacture of ac i d steel must be practically
fr e e from sulphur or phosphorus O n th e other hand or e s r i ch
i n phosphor u s may be us e d for th e manufactur e of basic steel
I n normal blast—furnac e work n e arly the whole of t he phospho rus
presen t in the or e goes into the p ig
F or steel making purposes the relative value of iron ores as
regards their phosphorus contents depends on the process i n view
F or th e Bess e mer acid process or e s r is e in val u e i n proportion as
th e phosphorus 18 low the maximum b e ing about 0 0 3 p e r cent
F or t h e Bessemer basic proc e ss the valuation is the reverse
A n average sample of pig for the basic process contains
-
.
,
.
-
,
,
.
.
-
.
,
.
.
-
,
~
,
.
,
,
.
.
P
Silicon
Sulphur
M anganes e
Phosphorus
er c
e t
n
.
,
0 0 5 —0 1 5
0 35 — 2 0 0
—30 0
,
,
,
Ore s
containing a phosphorus p e rc e ntage between th e abov e
limits ar e suitabl e for foundry work in wh i ch however an e xcess
of phosphorus is very obj e ctionabl e
-
‘
-
,
,
,
.
L
EA D
.
The most valuable and abundant ores of lead are gal e na and
c e russite which ar e generally found in veins in limestones
calcareous slat e s and sandstones and occasionally in gneiss
mica sch i st and andesit e Cer u ssit e in only found in th e shallow
parts of l e ad min e s G al e na usually contains a small proportion
of silver varying from 2 o z to 3 oz to hundr eds of ounces p e r
t on and i s commonly as sociated with blende and pyrit e
Th e world s produc t ion of l e ad amounts to about
short tons of which the Unit e d S tat e s dom e stic ou tput is e qual
to 2 6 per c e nt of t he whole The other chi e f producers of l e ad
1
are Spa i n G ermany M exico a n d N e w S outh Wal e s
The Broken H i ll Proprie t ary Company ( L imited ) in Ne w
S outh Wales is th e mos t productive lead mine in the world
L ead ores ar e purchased by smelt e rs on the fir e assay
1
T h e M ine ra l I n du stt y v ol x iii 1 90 4
,
,
,
-
,
,
,
.
-
.
,
.
.
,
.
’
’
,
.
.
,
,
,
.
,
'
,
.
-
.
,
.
,
.
1 70
MININ G GEOLOGY
M I CA
.
.
M ica is a cons t ituent of many rocks but only possesses a
commercial value wh e n it occurs in blocks or mass e s that are
capable of b e ing spl i t into sheets a square inch or mor e in size
Th e valuable d e posits ar e not abundan t and occur generally in
p e gmatitic veins in grani te and in micaceous gn e iss in hornbl e nd e
and mica schist Th e veins vary from a f e w inches to s e v e ral
,
.
,
,
-
.
hundred feet thick
These pegmatite veins or dykes as some writers suppose them
to b e c onsist of the thre e ess e ntial min e rals — quartz felspar and
—
mica in varying proportions They commonly r e semble a coars e
granit e and in general the best mica is found in thos e veins in
which th e constituent min e rals hav e crystallised in larg e masses
Wh e re the f e lspar and qua rt z are in small mass e s the mica is
usually of little valu e Th e Canadian mica is found in apa t it e
Valuable mica occurs in th e vein in rough crystals call e d blocks
or books sometimes e v e nly distribut e d t hroughout th e mass a t
oth e r times near the contact with th e country rock
M ica when found on the surfac e is soft and cracked Clear e r
—
and better coloured mineral is found low e r down in the solid 5 a n d
th e harder and more uniform the rock formation th e bett e r is th e
mica in colour and substance
I n other words th e quality
improves with the depth
V eins under 2 fe e t in width seldom contain mica of commercial
value exc e pt as scrap mica
As a g e n e ral rul e not more than 10 per cent of the mica min e d
is c apable of being c u t into plat e s the balanc e b e ing waste or
scrap mica 111 some m l n e s in the Un i t e d S t ates the yield of
1
sheet mica is l e ss than 3 p e r cent
I ndia and Canada ar e th e chi e f sources of the mica us e d in
E urope and the United States The latter country contains mica
d e posits in many places but f e w ar e of co m mercial value a n d at
pr e sent the supply for dom e stic us e is ma i nly d e riv e d from I ndia
111 th e mica mines of B e ngal in I nd i a t he b e st m i ca is found in
ro ck Th e gr e at e st demand ther e is for sh ee ts of the ruby
colour e d var ie ty from 3 square inches upwards
Sheet m i ca is larg e ly used for furnac e and stov e windows and
doors lamp protectors and insulators for electrical mach i n e ry
F or furnac e and stove doors and windows t he mater i al must b e
clear and fr ee from spots Th e cho i cest is in blocks of win e
colour whit e mica b e ing pref e rr e d next Biotite or black m i ca is
of lit tl e value T h e sta ndard sizes for the purposes stat e d abov e
range from 15 in by 2 in up to 8 in by 10 in S mall e r sizes
1
Was h i ngton 190 1
M in e r a l R e ou r ces of th e U n ited S ta tes p 8 7 4
.
,
,
,
,
,
.
,
.
,
.
.
,
,
,
-
.
.
-
,
,
.
.
-
,
.
.
,
-
.
-
.
.
,
,
.
-
,
.
,
.
-
,
.
,
.
,
.
.
’
.
s
.
.
,
.
.
.
,
.
O R ES
MIN ERAL S C O N S I D ER ED
A N D
E
C O N O MI C ALLY
17 1
.
seldom pay for m i ning and pr e paration La rg e s i z e and fin e n e ss
of gra i n ar e essential cha r ac t ers
The bulk of th e mi c a plac e d on the mark e t is us e d for e l e ctr i ca l
purp os es p rincipa lly in t h e construct i on of dynamos alterna tors
transformers e tc F or thes e us e s th e sheets must be fl e x ib l e fr ee
from cracks capabl e of withstand i ng high temperat u res and must
b e non conducting a low percen tage of iron be i ng an essential for
t h e la t ter
Colour is of l i ttl e mom e nt but pe rfec t cl e avag e is of
”
th e high e st impo rta nce as e l e ctrical m ica must be of un i form
thickn e ss and i s oft e n gauged to th e t housand th pa rt of an inch
Th e following co mmunica ti on r e c e ived by the Ag e n t G e n e ral
in L ondon for S o u t h Australia from M essrs N athan
Co of
L on don gives so me us e ful pa rticula rs as to t he pr i c e and mark e t
1
co ndition of mica
“
A l l th e sizes which the native crysta l will yield ar e at pr e sent
readily sal ea bl e by auction at p r ices ranging from 3d p e r po und
for 2 in by 3 i11 to 78 6d per pound for 8 in by 1 2 in Thick
1
n e ss must not exc e ed 1 in Anyth i ng from 7 3 ih to g in is
sa l ea bl e All qual iti e s are saleabl e bu t i t is obviously i mposs i bl e
to give an e s t ima te of probabl e pric e s as no two prop e rt ie s yi e l d
precisely s i milar mica and it would b e necessary to s ee a ca s e or
t wo of th e actual s t u ff b e fore any th i ng approaching a fi n a l
j udgm e n t co uld b e passed upon it
O n e or two important points may be made
Th e mica crystal s
after being split may be trimmed with ord i nary hand s hea rs all
cracked edges b e ing r e moved D o not was te th e mater i al by
aiming at regularity of shape but as far as possibl e w i t hout
such wast e r e m e mb e r that r e cta ngular plates are pr e ferred
Th e chi e f thing to s e cure is soun d ar e a wi t hou t crack s for it is
obvious tha t even mic ro scopic cra cks would m i l itat e agains t a
mat e rial to be us e d as an elec t ric insulator
Th e n e xt in impo rtance is to s e cur e a perfe c tly flat surfac e on
split t ing th e mica i n t o sh eets Any lumps or un e v e nnes s b et w ee n
th e laminae ar e du e to hydration or of te n to m etall i c i ns e rt ion
a n d the latt e r shows i tself in spot s
M ica w i th m e tallic ins e rtion s
is us e d for a vari ety of purpo ses but i s us e l e ss for insulating
.
.
‘
,
,
,
,
,
.
,
,
-
,
.
,
,
,
.
-
,
,
,
.
,
,
,
.
.
.
,
.
.
.
.
.
.
.
.
.
,
,
,
.
,
.
-
,
,
.
,
,
,
,
.
,
.
’
‘
.
,
.
.
,
Summarising
Avoid marginal cracks
1
6
i
i
n
S
pl
i
t
to
a
t
hickn
e
ss
of
to
n
( )
15
1
0 ) Avoid uneven plat e s as far as poss i bl e
(
d
( ) Cut in recta ngular plates as far as poss i bl e
e
( ) Throw out broken plates alto ge t h e r t hey w i ll
a
fr
e
ight
and
charg
e
s
p y
1
T h e N e w Z ea la nd M in es Rec or d Feb ruary 1 90 5 p 2 99
.
“
.
.
.
.
.
,
,
.
.
172
MININ G GEOLOGY
.
F or some purpos e s small irregular pi e c es of mica otherwise
usel e ss are cemented together and built up into sh e e ts of any
,
,
,
desired size and thickness
G round mica is used as a lubri cant and for decorative pu rpos e s
The greatest care must b e exercised in the preparation of mica
1
T h e sheet sho u ld be about 4 in thick and cut
for th e market
cleanly and sharply into r ectangular shapes if possible
The plates should be tr i mmed so as to c u t away any crumpl e d
or fla we d pieces and sorted ac c ording to their colour
The pr i c e of mica va ries a cc o rding to its size and c olour I t
rises rapidly with increase of size ; thus E nglish pri c e lists quote
sh e ets 2 in by 6 in at 2 8 6d per 1b and 3 in by 6 in at
.
.
.
.
,
.
.
,
.
.
.
68 6d p e r 1b
.
.
FI G
.
69
.
a,
.
.
.
,
.
.
.
—S ec tio n th ro ugh
Peg m tite Vei n ( A fter H K S ott
M et m o rp h i c h i t 5 b de o m po ed peg m tite with
m i a book 5
q rtz
a
a
s
sc
.
c
,
s
c
c,
s
ua
M O L Y B D E N UM
c
.
.
.
)
a
.
.
The comm e rcial o res of this metal are molybde n ite the sulphide 5
molybdit e t h e yellow oxid e 5 and to a small extent wulfenite the
molybdate of l e ad
M olybdenite occurs in beds or diss e minated in scales through
out crystallin e rocks such as granite gneiss and granular lim e
stone I t is produced in co m mercial quantit i es in California and
Canada I n th e Haliburton district in O ntario it o c curs in
quartz veins commonly associated with pyrites pyrrhotit e and
chalcopyrite
A t Wolfram Camp in the Hodgkinson G ol dfi e ld Queensla n d
molybd e nit e has been found in payable quantities in c l e an whi t e
1
0 11 th e O c currenc e o f M i c a in B ra zi l a n d on its
H Ki l b u rn S c ott
”
Preparation for th e Market T r a ns I nst M in a nd M et vol xi 1 902 3
,
,
,
.
,
,
,
.
.
,
,
,
,
,
.
,
.
,
,
,
-
,
.
.
.
.
.
,
.
1 74
MININ G GEOLOGY
.
has been attended with great success during the past few years
and the production of nickel has be e n so large that the monopoly
so long enj oyed by the N ew Caledonia mines has been complet e ly
brok e n u p
I n addition to nick e l the Sudbury ore contains copper about
and cobalt about 0 8 per cent and a littl e
2 8 p e r cent
platinum about 1 o z in 10 00 lh of nickel matt e
I n the S udbury district there is no regular vein system The
ore bodies occur separately or in detached groups
The d e posits are commonly lenti c ular pinch i ng out in both
directions and conforming to the general strike of th e enclosing
Huronian schists The ore always occurs in and contains frag
ments oi a basic and altered eruptive of the gabbro type relative
to norite
1
Accord i ng to C W D ickson the ore bodies occ u r either We ll
with i n this erup t ive or at its contact with th e oth e r pr e va i ling
rocks of the d i strict namely grani te or granitic gneiss quartzi t e
or th e metamorphosed repres e ntative of a series of basi c sed i
m e n ta rie s 11 0 W termed gre e nstones by the Survey of Canada
,
.
,
.
.
,
,
.
.
,
.
-
.
-
,
.
,
°
,
.
,
.
-
.
.
-
,
,
,
,
.
,
70
.
—
S ec tio n
o f O D e po it at Copper Clifi ( A fter J
H uro i n h i t 5 b D iorite (n orite ) 5 Py riti
n a
a,
H Co l li ns
bo dy
'
re
s
s s
sc
.
,
)
.
c o re -
c,
?
.
Three main belts of these norites and associated micro pegma
t it e s are n o w recognised des i gnat e d as the N or th e r n Mi d dle and
Southern belts respectively
They are at present mapped as
s e parate bu t gen e tically and mineralogically t hey are e ss e nt i ally
identical E conom i cally the Southern bel t i s the most important
-
,
,
.
,
,
,
,
.
.
1
O
.
I
.
,
xxx v
T h e Ore
-
Depo s its o f
i p 3 , 1 90 4
M E , v ol
J H C ll n s , Qu a r t J o u r G eo
n s t.
2
W D i c k s on
“
.
.
,
,
o i
.
.
u
.
.
.
b ry O tario
S ud
.
.
S oc L
.
o nd
on ,
n
,
v ol xl i v
.
.
,
T r a ns
.
A m
p 8 34 , 1 88 8
.
.
.
AN D MIN ERAL S C O N S I DER ED E C O N O M IC A LLY
O RES
175
.
genesis of t he pyrrhotite of Sudbury is still a question of
Acco rding to som e write rs includ i ng V ogt it i s du e to
doubt
t he d e v e lopm e nt of magma t ic differentiation in a c ooling roc k
magma
That many d e pos i ts of magnetite chromite and
corundum hav e originated in th i s way is almos t c e rtain 5 bu t
tha t m etall i c sulphid e s can separate out as primary con sti t uents
of a rock magma is s t ill op e n to doub t
1
Phil i p Argall cons i d e rs th a t th e nick e l and copper were leached
out of t he nori t e i n which they w e re ori g i nally form ed and con
c e n t ra te d along zones of fra c t ure by a p roc e ss of replacement a view
3
supported by Profess or Be ck of F re i b e rg who mainta ins t hat th e
br e ccia ted nature of th e ore must have be e n due to depos i t i on
during or after the m e tamorph i sm
The most i mpo rtan t us e of nick e l is in t he manufacture of
nickel steel conta i ning about 3 5 per cent of n i ckel Cons i derable
quan ti t ie s ar e used for pla t ing iron goods and i n the co i nage of
the Un i ted S ta tes and many E uropean co u n t ri e s
Th e
,
.
,
,
.
,
-
.
.
,
,
.
,
,
-
.
,
.
,
.
O I L S HA L E
-
.
Th i s occurs in beds or laye rs as membe rs of a s tra tifie d forma
tion It yi e lds m i n e ral oil by slow d i st i llat i on
The orig i n of the hydro carbon a ceous ma t te r in these shal e s is
I n many cases it h as b e en shown by m i cro
s om e wha t obscure
scop i c observa ti on to be du e to accum ul a t ions of gela ti nous algae
wh i ch lived in s hallow fr e sh wa t er lak e s and lagoons
Th e shal e de pos it s i n t he L othians of Sco tland ar e of grea t
3
e x t en t and of poor qual ity Th e B roxbur n shal e s yield from
2 4 to 30 gallon s of cru d e o i l and 4 2 lbs of ammon i um sulpha t e
p e r ton wh i l e th e D r u ms h or e la n d shal e s yi e ld 2 0 gallons of
crude o i l and abou t 6 0 lbs of ammonium sulpha t e The in du s tr v
i s maintain ed by th e product i on of bye produc t s
Th e Fe rmo carboniferous shales of N ew South Wal e s ar e of
high grad e but occur gen e rally i n thin seams Th ey are now
n e arly e xhaus t ed
Th e o i l shal e s of Ne w Zealand are of Mi ddle T e rtiary ag e
Th e y ar e i n pl a ces of great exten t but gene rally poor and low i n
a m monia
.
.
-
.
-
.
-
.
,
.
,
.
.
-
.
-
,
.
.
-
.
,
,
,
.
P
E T R O L EUM
.
Mi neral o i l is found i n geological formations of all ages but i n
commerc i al quan ti t i es occurs c h ie fl y in two horizons— nam e ly
t h e Mi d dl e Pal aeo z o i c a n d low e r half of t he T e rt i ary
P
C l S
S c De em ber 1 893
k L h
d
E l g
1 90 1
t it t
R B
E g v ol xx ii p 5 8 1 1 90 2
T
n
I
t Mi
,
,
.
1
r oc
o
.
3
.
o
.
c
,
.
'
.
3
e
.
ra
ec
s
.
e
,
ns
.
re vo n
n
.
en
u
.
rz a
,
.
e n,
e rs c
.
.
.
,
.
17 6
MININ G GEOLOGY
.
I n Ameri c a it is found mostly in rocks ranging from S ilurian
to Carbonif e rous and in E astern E urope and Asi a in ro c ks of the
E ocene and M iocene periods
G enerally speaking petroleum is found beneath the crowns of
anticlinal folds saturating porous unc e mented sandstones
The genesis of natural oil has not y e t been satisfactorily
e xplained The F rench school maintain that it is chemica l
r e sulting from the r e action of alkali metals at a h i gh temp e rature
0 11 steam and carbon dioxide
Crude petroleum in many r e spects
the same as natural oil was prepared synthetically by Ber t helot in
th i s way Th e hydrogen of the wat e r and the carbon of the
carbon dioxi d e hav i ng been deprived of th e ir oxygen unite to form
an oily substanc e closely r e sembling rock oil
Th e d e structive d i s t illation of shal e peat w ood and animal
matter prod u c e s an o i l having the same carbon and hydrog e n
compounds as the natural oil of Pennsylvania But 0 11 the oth e r
han d oils have be e n fou n d in Canada Tennessee and elsewher e
of a d i ffe rent compos i tion fi llin g cavities in a richly foss i liferous
rock The rock in wh i ch the oil is imprisoned is a thickly b e dd e d
lim e stone of Silurian age probably d e posited in a d e e p sea swarm
i ng with animal lif e I t is gene rally ass u med that the oil wh i ch
,
.
,
.
,
.
,
.
,
,
.
,
-
.
,
,
,
,
.
,
,
,
,
.
,
,
.
can apparently b e liberated only when the rock is broken is
indigenous to th e rock in wh i ch it occurs
The porous o i l bearing sandston e s of Pennsylvania are under
lain com for m ab ly by a formation of shale more than 1 0 0 0 f ee t
t hick containing fossil animals and fossil seaweed in vast quantiti e s
E xp e riments hav e shown that th i s fucoidal shal e wh e n subj e ct e d
to slow destructive dist i lla t ion in some cas e s yiel ds as much as
5 0 gallons of crude o i l to the ton of rock
This o i l in many
resp e cts can hardly be distinguished from the natural crude o i l
The commonly accepted theory is that petrol e um is a na t ural
d i st i llate from carbonaceous or a n i mal remains imprison e d in rocks
The distillate would naturally rise into the ov e rly i ng strata wher e
it would b e come c ondensed 5 and where the rocks w e r e porous i t
would accumulate
The heat required for the dist i llation may hav e b e en d erived
from igneous in t rus i ons plutonic or volcanic from t h e r e act i ons
of d e ep—seated metamorphism or from the heat due to pres
sure i n cases where th e s t rata have been involved i n d e ep crust
folds
Mi n e ral oil i s produced i n vas t quantities in the Unite d States
particularly in the States of Pennsylvania Texas O hio Cal i fornia
a n d I ndiana ; in the Baku region i n Southern Russ i a 5 G alicia in
Austr i a ; Roumania Burmah Borneo Sumatra a n d J ava
The output of the Appala c h i a n oil fi e lds in Pennsylvania a n d
,
.
-
,
.
,
,
.
.
.
,
.
,
,
,
.
,
,
,
,
,
,
,
,
,
,
,
-
.
MININ G GEOLOG Y
1 78
.
The once famous beds of South Carolina ar e considered to be of
1
Post Pliocene ag e
Th e phosphate of lime formerly work e d a t Aruba and Sombrero
in t h e West I nd ie s was or i g i nally a coral l i m e s ton e conv e rte d
into a phosphat e by the p e rcol a t i on of water containing phosphoric
ac i d de rive d from t h e ov e rlying deposits of b i rd guano
A valuabl e de pos it of rock phospha t e was d i s c over e d i n 1 90 1 a t
2
Clar e n don i n t h e Province of O tago in N ew Z e alan d I t occurs
in ch e m i cally e ro ded pock e ts and hollows on th e upper surfac e of
a Mi oc e ne l i m e s tone as shown i n th e following d i agram
-
-
.
,
,
-
.
-
,
.
,
,
FI G
A
L oo se
,
ph os l
i
71
.
.
— S e ctio n
o f Cl re don R o k ph o ph ate
d 5 B ro k ph o p h te 5 C l i me to n e g nerally
oniti 5 D gla on iti c gr e
d
h a t ic s a n
gl
au c
s
a
c
,
c
n
-
a
s
s
.
s
,
uc
,
-
c
e
nsa n
e
,
s.
The geological conditions wh i ch accompany and doubtl e ss
determ i n e th e e xist e nce of workabl e d e posi ts of phospha t e ar e th e
presenc e of a pho s pha te b e ar i ng format i on at th e surface lying in
a favourabl e posi ti on for un de rground w eath e ring ov e r cons i der
able areas a n d subsequ e n t concentrat i on of phosphate by replac e
m e nt or s e condary e nrichmen t
Th e phospha te d e pos it s in York e s P e n i nsula South Australia
occur in cav e s and fi s s u r e s i n a Cambr i an l i m e stone Th e y ar e
r e por t e d to be of large e xt e n t high grad e and favourably s i tua te d
3
for working
To b e come of comm e rcial valu e a phosphate deposit should f u l fil
the follow i ng r e quir e ments
-
,
,
.
’
,
,
.
,
,
.
-
of such magnitu de as to j ustify th e e rection of tramways
and o t h e r surfac e plan t nec e ssary for d e velopmen t and
winning of mineral
1
B
( )
e
-
.
Pe o e
J P rk
xxxv p 391
1
nr s
3
a
.
.
3
.
H Y
.
A u s tra l ia
.
,
U S G eol S u r v ey B u ll etin , N
“
h s ha s
T he R c
f
’
.
,
.
.
o
.
46, p
o k p o p te o O tago
6 0 , 1 8 98
T r a ns N
.
.
-
,
,
L
S
.
1 90 2
wn ,
Bro
.
N
ote
u pp l e m e n ta r y
s on
.
,
.
Z
I
.
,
vol
.
Iron a n d P h o s ph a te Depo sits o f S o uth
Recor ds 1905 p 5 A del a i de
th e
M ining
ns t
,
,
.
.
,
.
AN D MIN E RALS C O N S I D ERED E C O N O M I CA LLY
0 112 s
179
.
of h i gh grad e av e ragin g not less t han 5 0 per cent of
t r i calcic phosphate befor e dr e ss i ng
3
I
n
a
po
s iti on easy of access to a ra i lway or s e aboard
( )
—
E
asy
t
o
win
t
ha
t
i
s
in
a
pos
i
tion
in
wh
i
ch
i
t
can
b
e
4
)
(
work e d wa ter—fr ee by op e n cuts a n d quarry i ng Th e
ov e rburde n mus t also b e shallo w and e as i ly r e mov e d
Wh e n it e xc ee ds 20 f eet th e cos t of s t r i pp i ng run s a wm
w it h th e p ro fi t
2
B
( )
e
,
.
.
.
,
.
.
°
.
I t is on ly in e xc e p ti onal cas e s t ha t i t pays t o m i ne phos pha t e by
underground work i n g s A t Ross F arm i n P e nn s ylvan i a dur i ng
t h e y ear 18 99 2 000 long tons w e r e min e d from a s t ratum 30 feet
th i ck 4 000 f eet long a n d i ncl i n e d a t an angl e of 60 from t h e
hori zon ta l The stratum was mined to a dep t h of 30 0 fe et b e low
—
water l e v e l a n d averag e d abou t 5 6 p e r cen t of phospha te H e r e
t h e ma t rix consis t ed of a y e llow marl e as i ly a n d cheaply brok e n
The produc e rs how e v e r d id no t comp ete in d i s ta n t mark e ts w it h
t h e h i gh e r grad e s of phospha te from Sout h Carol i na T e nn e ss ee
1
a n d Flor i da but l ooked only for a r e mun e ra ti v e local mark et
,
.
,
,
°
,
,
.
.
,
.
,
.
,
,
,
,
,
.
P LA T I N UM
.
Th i s valua ble m etal is g e n e rally found sparingly d i ssemina t ed
in olivi ne in ol i v i n e gabbro s e rp e n ti n e and o t h e r ul t ra bas i c rocks
3
i n Rus s ia G e rmany F ranc e and Ne w Z e aland I t i s foun d in
gold plac e rs i n many part s of t h e world i n small quan tit ies
It is commonly assoc i a ted w it h chromi te of i ron which also has
a pr e f e r e nc e for magn e s i an erup t ive rocks
Pla t inum as sperryl ite t he ars e n i de of platinum occurs in t h e
cupri fe rou s n i ck e l ores of Sudbury i n Cana da a n d i n th e cop pe r
or e s of Ramb le r Mi n e i n t h e M ed i c i n e Bow M oun ta i ns of Albany
Coun t y in t h e S ta te of Wyoming R e fi n e d m ethods of analy s i s
hav e shown t ha t th i s m etal i n m i nu te t rac e s e x is ts i n cupr i f e rous
—
sulph i d e or e s i n many pa rts of the worl d
Hunde shag e n records th e occurr e nc e of pla ti num in Suma t ra
m wollas ton ite wh i ch i s as soc i a te d with sch i st s gran ite a n d
aug ite d i or ite He t hinks t ha t th e or e d e pos it was or i g i nally a
big l e ns of l i m e s to n e i mb e dded i n t h e sch i s t s s u bsequ e n t ly al te r e d
to garne t a n d wollasto n ite and min e r alised by ho t soluti ons carry
i ng copper g old and pla ti num
Th e worl d s suppl y of plat i num is ma i nly d e rived from placer
d e po s i ts in t h e Ural M oun ta i ns mos t ly s it ua t ed on t h e w e s te r n
-
-
,
,
,
,
,
,
.
.
,
.
,
,
,
-
,
,
,
.
,
.
,
,
-
-
.
,
,
,
.
,
’
,
1
3
3
2 13t A
J
L
F
S
.
.
.
.
R ep t U S G eol S u r ve y , p 4 94 , 1 8 99- 1 90 0
m , B u ll U S G eol S u rvey , N o 1 93, p 7 2
u n d sh a
n , T T a n s I ns t M i n a n d 111d ,
l
nnu a l
Ke p
H e
.
.
ge
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
v o xiii
.
.
1 90 4
.
18 0
MININ G GEOLOGY
.
slopes I n 1 90 4 the output of Russia amounted to
lb s
equal to about 90 p e r c e nt of the world s produ c tion
In
S e p t ember of tha t year two lum ps of plat i num were found a t
K r e s to wos d wis c h e n s k on e weigh i ng 7 5 6 lb s the other ov e r 3 60
lbs
A small part of the domest i c r e quir e men t s of the Unit e d
States is obta i ned as a s e condary product from the gold plac e rs i n
Trinity and Shasta Count ie s in Cal i fornia
Som e of the gold plac e rs of Colombia Alaska S i beria Austral i a
a n d Ne w Zealand con ta i n plat i num but rarely in payable quant ity
Th e Fifi e ld G oldfie ld i n N ew South Wal e s yi e ld e d in the y e ar
111 th e sam e year
1 90 2 3 7 5 o z of pla ti num valued at £ 7 5 0
Russ i a prod u c e d
which repr e s e nt e d ov e r 90 p e r cent
oz
of th e world s outpu t The balanc e i s mainly furn i shed by t h e
State of Colomb i a i n South America
.
,
,
.
’
.
.
.
,
,
.
-
.
-
,
,
,
,
.
,
,
,
,
,
,
.
.
.
,
.
’
.
,
.
K
U
I
C
S I LVER
Q
.
The only valuable or e of this metal is cinnabar the sulphid e
wh i ch occurs i n veins trave rsing slates and san dstones or d i s
seminated in al te red an desites I t is however found in rocks of
all ag e s and all k i nds but shows a preference for sa ndstones and
i n mos t cas e s is found alon g lines of country t ha t have been
affe cted by volcanic disturban c es
Some c i nnabar has b ee n d e pos i ted from hot solutions bro u gh t
up by volcan i c spr i ngs A t O ha e awa i Hot Springs in Ne w
Zealand th e cinnabar d e pos i ts were formed in this manner as
probably w e r e thos e of Almaden
The pr i nc i pal quicksilv e r prod u cing min e s at the pres e n t time
ar e s i tua t e d at Almaden in Spain Ne w Almaden in Cal i fornia 5
I dria in t h e Provence of Carniola in Austria ; a n d Russ i a
Th e averag e yield of the Almaden or e s is from 7 to 10 per cent
but or e s con t a i n i ng as little as 1 p e r c e nt hav e b ee n m i ned wi t h
r ofi t
The
grade
of
th
e
Russian
or
e
i
s
g
e
nerally
u nder 1 p e r
p
cen t
,
,
,
,
.
,
,
,
.
,
.
-
,
,
.
-
,
,
,
,
.
.
,
.
.
.
S I LV ER
.
Among t he principal or e s of silv e r are ke r a rg yr it e or horn
s i lv e r embol i te and argen ti te t he subsulph i d e
L arg e mas s e s
of th e t wo form e r were found at the Brok e n H i ll m i nes in N ew
Sou t h Wal e s d i s s e mina t e d throughout kaolin clay
M asses of na t ive silv e r have be e n foun d in S axony a n d Har t z
M ounta i ns but th e larg e s t masses we re d i scover e d i n Me x i co a n d
P e ru a n d i n th e L ak e S u p e r1or min e s assoc i ated with nativ e
copp e r
,
,
,
,
.
,
'
,
.
‘
,
,
,
.
182
MININ G
G
EOLOGY
.
slat e s ar e of te n infe rior in durab i lity M arcasit e 1s obj ectionabl e
in slat e as it oxidis e s readily Cubical pyrit e s do e s not oxidis e
r e adily and is ther e for e not so obj e ctionabl e
A goo d s la t e should b e capable of b e ing spl it into smooth thin
lamin ae parallel to the plan e s of slaty cl e avag e
The s p e c ific gravity of slat e vari e s from 2 7 to 2 9
L arge quant i ties of slate are quarried in the Unit e d S tates
F rance and E ngland
.
.
,
.
,
.
.
,
.
,
S U LPH U
R
.
sulphur of comm e rc e is d e rived from native sulphur and
T he
pyrit e s
N ativ e sulphur is common in most volcanic region s mor e
e sp e cially around th e vents and fi s su r e s both activ e and e xtinct
Th e world s production of native sulphur in 1 90 4 amount e d t o
tons of which I taly produced over 93 per cent Th e
balance is mined in Japan United States F ranc e Austria a n d
G re e ce
Th e price of crud e sulphur vari e s according to quality from
£ 3 to £ 4 per ton
The sulphur is principally used in the manu
facture of sulphuric acid
The principal producers of pyrit e s for th e manufactur e of sul
h
r ic ac i d ar e Spain F ranc e
United
tates
G
er
m
any
N
u
S
or wa y
p
I taly Canada and Russia
.
,
,
.
’
,
.
,
,
,
,
.
°
.
.
,
,
,
.
,
,
,
,
T ALC
.
This min e ral in its fib rou s and massive forms occurs in beds
and l e ns shaped masses in ta lcose and chloritic schists I t is
often associated w ith granular limestone
Th e massive form is gen e rally known as steatit e or soapston e
Talc is used as fl ou r talc and as piec e s cut i nto various
Th e fl ou r is us e d as a base for fi r e p roo f paints for e l e ctric in
s u l a t or s for boiler and s t e a i n pipe coverings as a bas e for dyna
mi te in the manufactur e of wall pap e r for l e ather dr e ssing and
as a lubricant
T h e harder vari e ties of soapstone are cut into h earthst on e s
l i nings for fur naces laboratory tabl e s ov e ns pencils and gas
t i ps Th e talc produced in th e United S tates is valued at abou t
£ 3 5 s per ton
-
.
.
.
.
-
,
,
-
,
,
-
,
,
,
.
,
,
,
,
,
.
,
.
.
T H O R I UM
.
Th i s rare and valuable metal is obtain e d from the min e ral
monaz i te which is essentially an anhydrous phosph at e of th e
rare e arthy metals c e rium l a n t hanum and di dymium having the
,
,
,
,
O RES AN D MIN E RALS C O N S I D ERED E C O N O M ICA LLY
18 3
.
formula (Ce L a D i) P O 4 A small but var i abl e propor t ion of thoria
h
I S n e arly always pr e s e n t
T
O
(
1
M onaz i te i s d e scr i b e d by J H Pra t t as l i gh t—
y e llo w hon e y
y e llow red d i s h brownish or y e llow i sh gre e n in colour w it h a
r e s i nous to vi t r e ous lus t re It i s t ransluc e nt to sub t ran s luc e nt ;
bri ttl e w it h concho idal fr ac t ur e and hardn e ss from 5 to 5 5 :
monocl i n i c and i n crystals up to 2 in long P e rfe c t crys tals ar e
generally small from g i n to T 3 i11 do wn wa rd to t hos e of m i c 1 o
sc op i c s i ze Th e spe c ific gravity i s h i gh a n d rang e s from 4 6 4
to 5 3
It i s incompl etely in s oluble in hydrochloric ac i d bu t compl et ely
and readi ly i n sulphuric acid I f oxal i c acid is ad d ed to t h e v e ry
dilu te fi lt e r e d s u lphuric acid solut i on or to t h e solu ti on ob ta i n e d
by fusing the min e ral wi th soda and i f t h e m a ss is t r e a te d wi t h
wa te r a n d the r e s i du e fi lte r e d a n d d i ssolv ed w it h hydrochlor i c
acid a pr e c i pi tate i s ob tain e d wh i ch upon igni t ion b e comes
brick re d due to t h e pres e nc e of c e rium ox i de
B e for e the blowp i p e the m i n e ral t ur ns gr e y bu t is infus i bl e
I f h eated with s ul phur i c acid it colours th e fl a m e blu i sh gr ee n
due to ph osphor i c acid
M onazite i s found i n granite gn ei ss i c rock s a n d m ica sc h is t in
th e Mar iti me M ountain s of Braz i l i n S o u th M ounta i n reg i on of
N o rt h Carol i na a n d many oth e r plac e s but only in minu te
quant ity The monazi te of commerc e is d e r i v e d from sands or
place rs r e sul t ing from t h e de nuda ti on of th e m i n e ral b ea ri ng rock
3
Th e Bra z i lian de pos i ts occur as b e ach sands
Tho r ium is c h ie fl y us e d in th e manufactur e of mantl e s for
inca nd e scen t gas ligh ts
Th e value of monazite is about 4d per po u n d
.
o
.
.
.
,
-
,
,
,
,
.
,
,
,
.
.
,
.
.
,
.
°
.
,
.
,
,
,
,
,
,
-
.
,
,
.
-
,
.
~
,
,
,
,
,
.
-
.
.
.
.
.
The only ore of thi s m e tal of comm e rcial valu e is th e oxi de
cass i terite wh i ch occurs i n lodes b e d s a n d stockworks a n d i n
alluvia l dr i f ts
Tin ore i s found i n grani te f e lspar porphyr y and oth e r a cid
e ruptives and in sed i m e n taries which hav e be e n in t rud e d by
gran ite et c
3
one of th e gr e a t e s t tin m i n e s 0 11 t h e
A t M ount B is c h ofi
glob e t he Pal aeozoic sla te s and sands t on e s ar e i n t rud ed by dyk e s
,
,
,
,
,
.
-
-
,
,
,
.
,
,
,
o ep H e P tt
W i gto
e
ote
P p et
t
M
n er a l R es ou r ces of
h
e
U
n ite d S ta tes , p
i
11 63,
r
a
d
J s h
,
y
n , 1 90 4
as h n
3
130 0 cit , p 95 1
3
B isc h o fi T in M n ,
s on t h e M u n
T r a ns
N
Fa v m s
S y dn y P
I ns t M i n a n d M e t” am h l , p 16 , L n d n , 190 5
1
.
.
.
.
.
.
.
.
.
,
.
o t
o o
'
.
i e
.
18 4
MININ G
GEOLOGY
.
of porphyritic f e lsite which c arries topaz both c rystallin e and
amorphous
Th e t op a z isa tion was probably a pneumatolytic
—
proc e ss proceeding from de e p s e at e d granit e The f e lspar of th e
ground mass is replac e d by topaz The analysis record e d by
Baron Von G ro dde ck showed no alkali Th e rock cons i st e d
practically of quartz topaz a n d tin Wolfram do e s not occur in
payabl e quant i ty in the topaz tin ore
The common associa t es of tin ore are wolfram quartz mica and
tourmaline
About 6 5 p e r cent of the world s supply is derived from th e tin
plac e rs in th e Straits S ettlements and D u tch E ast I ndies wh e r e
t h e tin bearing gravels cover hundr e ds of squar e m i les
The world s annual production is about
tons
Tin containing 5 5 p e r cent of arsenic is usel e ss for commercial
purposes and requir e s further purifying
Tin—ore is bought by the smelt e rs from the results of the dry
assay and is subj ect to certain sch e dule d e d u ctions
.
.
.
.
.
,
,
-
.
-
,
,
,
.
’
.
,
-
.
’
.
.
.
,
.
T UN G ST E N
.
The principal ores of tungst e n are sche e lite th e tungstate of
lime 5 wolfram the t ungstat e of iron ; and 111 e g a b as ite th e
tungstat e of mangan e se
Wolfram i s usually associated with tinston e S c h ee lite occurs
in v ei ns in schis t s and sa ndston e s generally associat e d with
quartz Wh e n th e v e in stuff con ta i ns gold or silver as often
happ e ns th e sch e eli te can be produc e d very cheaply as a
b y product
The b e s t known deposit of m e g a b a s ite is that i n th e I ma
M inin g Company s prop e rty at Patt e rson Cr ee k in th e s tate of
I daho wher e i t occurs with wolfram in a ve i n varyi n g from
5 f e et t o 1 5 f e e t wid e and assay i ng from 5 p e r cent to 5 0 p e r c e n t
of tungstic aci d
Th e princ i pal sourc e s of the world s tungsten are E ngland
Austria Hungary Saxony G ermany Ne w South Wale s and
Queenslan d
The pric e vari e s wi th th e quality of the ore G e rman and
E nglish buyers g i v e f rom 7s to 8s per unit
I n the Un ite d States prices are somewhat higher the val u e of
sch ee li te conta i ning from 4 5 p e r cent to 5 5 p e r cent of tun gs ti c acid
b e ing about 8s per un it whil e ores conta ining from 5 5 p e r cent
to 6 5 per c e nt of tungst i c aci d command 10 s p e r un it of scheel ite
The f e rro tungst e n ore wolfram is mainly prod uced in Cornwall
E
ngland
Hungary
Ne
w
South
Wal
e
s
and
Queensland
I
t
is
)
(
Wolfram to be mark e tabl e mus t
s ol d on th e tungs ti c acid basis
,
,
,
.
.
,
-
.
,
,
-
.
-
’
,
,
,
.
.
.
’
,
-
,
,
,
,
.
.
.
.
.
,
.
.
,
.
.
.
.
.
-
,
,
,
.
.
C H A P T ER V I I I
.
M I N E - S A M P L I N G A N D O R E -VA L U A T I O N
CO N
.
—
—
l
u
m
n
p
i
n
g
q
ip
e
t
S
a
m
E
S a m p l i n g I nterval s — Rec ord o f S a m p le s
T EN T S z
—B rea ki ng t h e S a m ple— S a m pl i ng— Redu c tio n o f S am p le— A s s ay o f
S a m ples — C al c u la ti n g V al ue— F ut ure P ro s pects — S a m p l e V a l ues a n d
M i l l V a l ue s S a m p l i n g D u m p s a n d H e a p s
-
.
the maj ority of min e s sampling proc ee ds s i multaneously with
the mine d e v e lopment th e results being recorded 0 11 a ssa y p la ns
which are generally longitudinal or stop e plans
Wh e r e the
sampling during dev e lopment has been car e fully and s y s te m a ti
cally don e the averag e s should approximat e those obtained by th e
mi n e —e xaminer
—
S a m p ling E q u ip m e n t
This include s n e w sample bags of
canvas or stout calico say 1 4 in long a n d 9 in wid e 5 a canvas
she e t about 6 ft long and 5 f t wid e 5 a short handled 4 lb or
5 lb hammer 5 a gad or two ; small linen tap e or foot ru l e ; a
numb e r of small metal tags or strips of soft wood each with a
distinc t iv e number or mark 5 and a stout canvas lock u p sack
for th e safe custody of sampl e s
S a m p l ing I nte rv a ls —B e gin th e sampling of a l e v e l at t he
end of th e main cross cu t or at som e po i nt e asily located with
r e sp e ct t o a surv e y station
Wh e n th e whole width of th e v e in or seam is expo se d 1n t he
drive it is customary to sampl e th e high e r or foo t wall portion
lying on th e back of th e lev e l as the lower po rt i on may b e par tly
und e rfoot and often covered wi th mud and wat e r
D ivid e t h e lev e l into se c tions of 5 f t 10 f t or more according
to t h e e xt e nt of th e op e n ground and charact e r of or e M ark
the divisions wi t h chalk or by blackening th e wall wi th a candl e
I
N
,
,
.
,
.
.
.
,
.
-
.
.
,
.
-
.
,
-
.
.
-
,
.
,
,
.
.
,
.
,
,
.
,
flam e
.
With r e spect to th e sampling intervals it is well to r e member
t hat a large number of small samples tak e n a t sho rt intervals are
often mor e reliable than a small n u mber of large sa mples taken at
wid e interval s
Wh e n the ore is known to b e consist e nt in valu e and is
,
.
,
186
MIN E S A M P L IN G AN D O R E
-
-
V
A LU AT I O N
1 87
.
xposed in long str e tche s th e sa m pl i ng intervals may be 2 0 f t
apar t ; but wh e n th e vei n i s som e wha t i rr e gular in w i dth a n d
valu e t h e 5 ft intervals will g i v e th e mos t tru s t worthy r e sults
—
o
S
Car e fully me a sur e and r e cord t h e
l
R e c rd O f
am p e s
wid t h of th e v e in in fe e t and inch e s at e ach i nterval
A simpl e and a c curate m ethod of r e cording t h e sampling
intervals w i d t hs and sa mpl e numb e rs i s to d raw a diagram in
e
,
.
.
.
.
.
,
,
FI G
d S m p l i ng Inte r l
o i g Reco rd o f Wi dth Value
Ou
fi e ld b ook repr e s e nting a longitudinal s e c t ion of t h e lev e l
th i s d i agram which n e ed no t be drawn to scal e all t h e n e cessary
i nforma t ion can b e shown graph i cally Th i s m ethod h as also
t h e a d van ta ge t hat the assay values can aft e rwa rds b e fille d in a t
th e di ff ere n t intervals thus completing the r e co rd
.
72 — S h w
n
.
s, an
s,
v a s.
a
-
.
,
,
.
-
,
V
V
FI G
.
73 — L
.
b
h
<0
'
o git di
n
.
u
V
‘
n al
S
m
m
V
0 :
'
b
v
h
00
c}
0:
co
09
cc
cc
ection o f B lo k between 15 0
c
an d
30 0
feet Le ve ls
.
The widths numb e rs and values ar e commonly r e corded on
m i n e assay plans in di ffer e nt coloured i nks accord i ng to th e
i n di v i dual fancy of the e ng i n ee r 5 but t his is not n e cessa ry in t h e
e xamin e r s fi e ld book which i s a p riva t e r e cord
I n th e above fig u re th e widths of ore ar e shown in inch e s und e r
,
,
-
,
’
-
,
.
188
MIN IN G GEOLOGY
.
the l e vel and the valu e in dwts abov e th e level The sampling
intervals ar e r e pr e sent e d by dots
1
M in e at J oh a n n e sb u rg th e
111 the M eyer and Charlton
values entered upon th e continuous s e ction are not th e assay
values bu t t he recovery valu e s whi c h the di ff e rent processes i n
use are est i mated to be capabl e of recovering
—
B re a k ing t h e S a m p l e D ress the face down with a pick so
as to e xpos e a fr e s h surfac e and i f ne c essary cl e an it with
water
With t h e hammer and gad br e ak a sample at each interval
allow i ng th e mat e rial to fall on to the canvas sheet or into a stiff
felt hat or narrow box held by an assistant
Th e sample is taken from a groov e cut at r ig h t ang les t o the
plane of t h e dip 5 or in oth e r words a cr oss th e thickness from
wall to wall as shown in fi g 7 2
I n cases wh e r e the width of th e v e in is l e ss than that of the
lev e l or stop e it is n e cessary to squar e t he or e on the back of the
level or stope in order that the true width of th e v e in from wall
to wall may be exposed for sampling
I n or e of fairly uniform hardness the width of the groove will
vary from 4 in t o 6 ii1 and from 3 in to l % in dee p T h e
sampl e will generally weigh from 2 lbs t o 1 0 lbs for every foot
of vein or b e d
Wh e n the v e in matt e r is arranged in distinct bands of c r u s tifi
cat i on — that is wi t h a ribbon structure — it is advisabl e to sampl e
e ach band s e parately to determine where the values li e
W i de lodes shoul d also be sampl e d in widths of 2 ft or 3 ft as
sometimes th e valu e s are carried by the foot wall por t ion som e
times by th e hanging wall or by the central portion I n s uch
cas e s a singl e sampl e taken from wall to wall may convey quite
an e rron e ous impr e ssion as to th e comm e rcial valu e of th e lode
Where a lev e l is driven on a wid e lode only a small portion of
th e or e is e xpos e d for examination
I n such cas e s it is customary
for th e manag e ment during th e progress of d e v e lopm e nt to cross
cut the lode at int e rvals of 2 0 ft or 5 0 ft according to th e
m et allif e rous character of the or e Th e se cross cuts w i ll a fi b rd
th e examin e r an opportun ity of sampl i ng th e lode from wall to
wall in such manner as th e cas e may r e quire Where there ar e
no cross cuts through the l od e from the level the ful l o r at any
rat e the payable width of ore will generally be found exposed in
t h e stopes
It of t en happens in the case of fi a t—lying veins that the l e vel
has been driv e n on th e footwall of the vein or that the level has
1
T A R i c k ard T h e S a mp lin g a nd Es tim a tion of Or e in ( 1 M ine p 1 74
.
,
.
.
,
,
,
.
,
.
,
,
,
.
,
,
.
,
,
.
,
.
,
,
.
,
.
.
,
.
.
.
'
.
.
.
-
~
-
.
.
.
,
-
,
.
.
,
.
.
.
,
-
.
.
-
,
,
,
,
,
.
,
,
,
.
N
ew
.
Y ork
,
,
1 90 4
.
,
.
,
1 90
MININ G
G
EOLOGY
.
groov e s cut at right angles to the plane of the d i p The thick
n e ss of ore i s m e asured and recorde d on a d iagram in the fi e ld
b ook togeth e r wi t h th e sample numb e r at each int e rval
—
o
S
Th e weight of th e sample broken
R e du c ti n o f
a m p le
down will vary wi t h the wi dth a n d hardness of th e or e Wh e n it
i s larger th a n t he capaci ty of th e sampl e bag th e sh ee t mus t b e
carri e d to a convenien t plac e und e rgroun d and its con te n t s
broken down to the si z e of a walnut When this has b ee n don e
t h e sampl e i s thoroughly m i xed formed i n t o a v e ry fl a t t runcated
con e and quar te r e d
T wo opposi t e quart e rs ar e r e j e cted be i ng r e mov e d c o mp le te ly
with all th e ir fi nes from the sh ee t The ma te rial in the t wo
r e main i ng quart e rs is th e n brok e n down t o a s i z e half th e d i am ete r
of a walnu t t horoughly mix e d and again quar te red Th e two
quar te rs ly i ng in the pos it ion of th e t wo quart e rs retained in th e
fi r s t op e ra ti on ar e r e j ec t ed a n d removed from th e s h ee t
A common m et hod of mixing th e ore on t h e sampling sheet i s
to toss the material from one s i de to th e other I n th i s process
care must b e t aken to insure that th e fi n e s are not concentrate d
in on e particular par t of th e sample but e v e nly distribu t ed
t hroughout the whole mass before e ach quart e ring
I n thr ee qu a r te rin g s a sample w eigh i ng 8 0 lbs will thus be
cu t down to 1 0 1b s which is about the maximum capacity of th e
sampl e —bags
The t im e required to break down a sampl e will depend upon
th e hardness and s i ze of the lode I t seldom i s l e s s than half an
hour a n d may ext e nd to several hou rs depend i n g upon th e
number of quar t e rings needed to reduce th e sample to a conv e nien t
we i ght Th e sampling of a large mine may occupy several week s
a n d run into a cost of sev e ral hundred pounds
A s s a y O f S a m p le s —The whol e of t h e sampl e should be dri e d
crush e d in a rock breaker in t he laboratory to pass through a
10 m e sh sieve mixe d a n d sampled by quartering t ill reduc e d to
a pound or t wo in w ei ght all of which sho u ld be fi n a lly p u lver i sed
pass e d t hrough a 60 mesh si e ve again mixed and d ivided into
two portions On e portion is handed to th e assayer wh i l e t h e
o t her is r e tain e d as a duplicat e sample for subsequent referenc e
and v e r ifi c a t ion if the n e c e ssity should aris e
Carelessn e ss in the labora t ory may stultify all the care exercis e d
in the sampling underground
I f th e mi n e examiner submit his samples to an assayer whos e
u a l ifi c a t io n s are unknown
to
him
he
should
t
ke
car
e
t
o
be
a
q
pr e sent dur i ng th e crushing pulverising and fi n a l division of th e
assay sampl e s
The d upl i ca t e sampl e s should be put in t o small cal i co or s tou t
.
.
,
.
.
-
,
,
,
.
,
,
.
,
.
,
.
,
°
.
-
.
,
.
-
,
.
.
.
,
.
.
°
,
,
,
,
.
.
,
.
-
-
,
,
,
,
-
,
,
,
.
.
.
-
,
,
.
,
MIN E S A M P L IN G A N D
O RE V
-
A LU AT I O N
1 91
.
brown pa per bags lab e ll e d
s e cured in a lock u p sack which
shoul d b e remov e d from the labora to ry
Th e e xam i ner s sampl e s shoul d never b e submitt ed to th e min e
assayer 5 a n d only i n very exc e p ti onal c i rcums t anc e s shoul d t h e
sampl e s b e placed in th e han ds of an unknown assayer
—
C a l c u l a t in g A v e ra g e W id t h a n d Va l u e o f V e in
Th e
a s s ay valu e s may b e expr e ssed i n p e nnyw e ights of gol d per ton 5
p e rc e n tag e of m e tal 5 o r in the cas e of low valu ed gold or bul li on
t h e mon e y valu e may b e s ta te d i n dol lars or 8 ( l p e r ton
Th e th i ckn e ss of t h e or e is mos t conven ie n tly e xpr e ss ed in
i nch e s for v ei ns up to 8 f ee t or 10 fe et th i ck Tak e t h e cas e of
te n sampl e s from a gold —b e ar i ng v ei n as follows
-
,
,
and
-
,
.
’
.
.
-
-
,
,
-
.
.
.
.
,
A
s s ay -
val ue
T o n in
p
n ny w e
h
Pe
p
er
ig t
I n ch—d w t
.
s
.
Th e av e rag e w i dt h i s foun d by di vid i ng t h e sum of t he wi dths
3
by t h e numb e r of sampl e s Th u s i n t his cas e we have T ? 35 6
i n ch e s av e rag e w i d t h
Th e av e rag e assa y val u e is foun d by d ivi ding t h e sum of t h e
inch dwt by th e sum of t h e w i dt hs as un d e r :
d wts
p e r ton for a w i d t h of 35 6 i nches
When a ve i n conta i ns t wo ban ds of payable or e se para te d by a
band of no valu e wh i ch cannot b e sorted ou t economically t h e
av e rage assay valu e is asc e r ta i n ed as follows
L et band A b e 1 8 inch e s wid e and hav e an as say valu e
of £ 2 per ton
B
6 i nch e s wi d e and wor t hless
1 2 inches w i d e a n d wor t h £ 3 p e r ton
C
.
,
.
-
-
.
.
.
,
,
,
.
.
.
18
per
10
11
1 92
MININ G G EOLOGY
.
I f it is practicable to sort out half of t he worthl e ss ban d then
t he av e rag e assay valu e of th e ore will be found as under
,
2 3S
8d P
.
.
er
t0 “
I n est i mat i ng the n e t p r ofi t in sig h t i n a block of or e i t is man i
f e st that th e r e covery valu e and not the assay value must form
th e ba s i s of th e calculation
H ig h A s s a y Va l u e s —A sample giv i ng an e xc e pt i onally
h i gh as s ay valu e may b e de alt with in d i ffe ren t ways It may b e
d i scard e d e n ti rely and not includ e d i n th e av e rag e 5 or asc e r t ain
t h e av e rage valu e w i t h i t include d and replace th e orig i nal e x ce p
t ion a l v al u e by th i s av e rag e and then calculate the average valu e
,
,
,
.
.
-
.
,
,
for
average width
F or e xampl e : F iv e Samples gave values of 10 dwt 2 0 dwt
2 5 d wt 1 2 0 dwt and 2 5 dwt per ton
The av e rage i s 4 0 dw t
Replac e the exc e pt i onal val u e 12 0 dwt by 4 0 dwt and then
proc e ed with t he calculation of resul t s
Th e exc e ptional value may r e present a small patch of rich or e
or a bunch of rich ore i ncreasing in d i mensions going upwards or
downwards or e ven a soli tary speck of g ol d The most sat i s
factory manner of d e al i ng with an e xc e ptionally r i ch assay from a
1
sampl e is to resample th e v e in a s e cond t i me T A R i ckard
also r e comm e nds the tak i ng of i n t erm e diat e samples as a fur t her
precaut i on against fraud or m i stak e
F u tu re P r o s p e c ts —When sat i sfac tory valu e s hav e b ee n
obta i n e d around a block of ground t he na t ural i nferenc e is that
th e area of ore is of the same approx i mate value
E xp e r i enc e has shown tha t wher e a block i s e xpose d on four
si des such inference is fair and reasonable Wher e the block i s
e xpos e d on three sid e s the infer e nce is op e n t o doubt
B e fore arr i ving at a de fin it e conclusion as to th e future
prospects of th e mine it i s advisable for th e e xam i ner or min i ng
e ngine e r to c ar e fully consider the following quest i ons
1
I
s
there
any
chang
e
of
rock
formation
enclos
i
ng
th
e
lode
( )
in any part of the mine ? I f so what in fl u e n c e do e s
this change of country e x e rcis e upon the value of th e ore ?
111
2
I
s
there
any
i
ndication
of
barren
zones
of
or
e
e
ither
( )
depth or hor i zontal extension along the cours e of th e
lo de ?
3
Ar
e
the
values
i
n
t
h
e
zone
of
oxidation
l
i
k
e
ly
to
be
mam
( )
ta in e d in the unoxidis e d portion ?
d
What
are
the
probab
i
lities
of
impov
e
rishm
e
nt
i
n
e
p
t
h
"
4
( )
T A R i c k ard Z oe cit p 4 2
th e
.
.
.
,
.
,
.
,
.
.
.
,
,
.
.
,
,
.
,
,
.
.
.
.
.
.
,
.
,
.
.
,
-
,
,
,
"
1
.
.
,
.
.
,
.
.
1 94
MININ G GEOLOGY
.
E
ach
block
can
now
be
sampled
separately
by
p
i
cking
( )
piec e s of or e from i ts four s i d e s
5
O
r t h e ma te r i al e xcavat e d from th e t r e nch e s can b e wh ee l ed
( )
to a cl e an p ie c e of ground s pawl e d in t o small p i ec e s
m i x e d and quart e r e d rep e at e dly unt i l a sampl e of con
v e n ie n t s i z e
i s ob t ained B e for e e ach quart e ring th e
larg e r pieces of ore must b e brok e n to half th e ir diam ete r
i n th e pr e c e ding quartering
0
r the mat e rial from the t r e nches can be crush e d in a rock
O
( )
break e r mix e d and quart e r e d down t ill th e assay sampl e
i s obta i ne d
S a m p l ing H e a p s O f T ai ling s —I f t he accumulation of
ta i lings i s larg e i t should b e sampl e d i n separate s e c t ions as
larg e piles of sands are liabl e t o vary consi de rably in valu e i n
a
.
,
,
,
.
.
,
,
.
.
,
d iff erent
parts
Stake o ff the heap so as to divid e it in t o sections about 5
yards square M ak e a diagram in fi e ld book corr e spon ding t o
s e c t i ons
Record t h e d i mensions of the sections and d i stinguish
e ach section by a l e tt e r as A B 0 etc
Sampl e e ach section b e g i nn i ng with s e ction A
at
1
W
i
th
a
sampling
i
ron
tak
e
ampl
e
all
ov
e
r
the
s
e
c
ti
on
s
s
( )
say every foot or two
2
I
f
t
h
e
r
e
is
r
e
ason
to
b
e
li
e
v
e
tha
t
t
h
e
values
ar
e
not
the
)
(
sam e from t op to bot t om put t he top mat e r i al into on e
bag a n d th e lower into ano ther 5 o r i f nec e ssary separat e
sampl e s can b e taken for e v e ry foot of d e pth
3
u
d
I
f
th
e
r
e
i
s
no
sampling
iron
availabl
e
holes
ar
e
a
t
g
( )
int e rvals of e v e ry 4 f ee t or 6 f e et Th e san ds from t h e
holes are whe e l e d to a clean place m i x e d a n d r e duc e d by
quartering to a conv e ni e nt size
I f r e quire d th e sand obtain e d from di ffe r e nt depths can b e
kept separate
“
—
By
S a l t ing O f M in e s
salting is m e ant the illegal
e nrichmen t of th e ore w ith th e obj e ct of giv i ng th e prop e r ty
a fi c t it iou s value
Th e m i ne e xamin e r should be fam i liar with the m e tho ds adop te d
by unscrupulous p e rsons so as to b e abl e t o pro te ct t h e in te r e s t s
of his principals
A common metho d i s t o t amp e r with t h e e xam i n e r s sampl e s ;
a n d for th i s r e ason t h e sampl e s shoul d always b e 111 saf e custody
unt i l th e assay r e sults are known
Cas e s ar e known where th e sample bags have b ee n e nriche d
befor e th e sampl e s were put into them It is t her e fore a wise
precaution to k ee p t h e sampl e bags i n a lock u p sack unt i l th e y
.
,
-
.
.
,
,
,
,
,
.
,
-
,
,
.
,
,
,
.
-
,
.
,
,
.
,
.
.
,
.
-
,
.
’
.
-
.
-
-
MIN E S A M P L IN G
AN D
-
O RE-V
A L U ATI O N
195
.
are requir ed A n d e ven then it is advisable to turn each bag
i nside out and shak e vigorously befor e us e
I n the case of gold mines sof t or e has bee n a rtifi c ially e nriche d
to a d e pth of a foo t or mor e wi t h a strong solu ti on of c h lori de
.
.
-
,
F raud has b ee n prac t ised on m i n e e xamin e rs by str e tc hes of
rich ore havi ng b e en sk i lfully buil t i nto t he wall of a l e v e l a t
d i ff e r e nt i n tervals and a t t he work i ng fac e t h e j o i n t s b e in g
obscured by libe ral splashes of m u d I n t h e same way a rt ifi c ia l
ou tcrops hav e b ee n prepar e d
D umps of ore hav e b ee n stac ke d w it h ri ch ore on t he sid e s and
top surfa c e A n impos t ur e of this k i nd is a t onc e d isclos e d by
t h e proc ess of tr e nch ing wh e n procur i ng sample s for assay
Sampl e s of gold wash i n te n de d for e xam i na ti on by panning
have b ee n e nrich e d e i t h e r b e fore or d ur in g th e wash in g by th e
ag e ncy of gold bea r i ng tobacco ash p e ll ets of clay a n d gol d
b e aring fi n g e r na i ls The gol d obta i n e d from t h e pa n ning of gol d
wash or ta ilings sho ul d b e e xam i n e d un der th e m i croscop e
Bul k sampl e s of ore hav e b e en sa lted dur i ng th e proc e ss of
t r e atmen t i n t h e ba tte ry e i t her by t h e ad diti on of gold or
-
,
.
.
.
.
-
,
,
-
-
,
,
-
.
.
,
Th e exa m in e r s samples may b e unlawfully e nriched a t any
stag e from t he break i ng of t h e mate rial i n th e m i n e to th e
assay i ng i n th e la b ora to ry S t rong solu t ion s of gol d chlor i d e
hav e b ee n inj ec te d i n to t h e bags w ith a syr i ng e a n d gol d du s t
adde d to t h e li t harg e a n d fl u x e s F raud is so e as i ly prac t ise d
in t his s tage t ha t th e e xam i n e r should eit her suppl y h i s own assay
mate r i als or te s t t hos e plac e d a t h is di s posal
I n t h e s e day s of min e valua ti on by sys te ma ti c sampl i ng cas e s
of s tac king or sa l ttng of t h e or e i n t h e min e ar e ra r e a n d e asily
circumven te d by th e wa t chful e xam i n e r But b e s i d e s cov e r t ac t s
inte nded to b e gu ile t he e xamin e r m a y be m i sled by t h e s u p pr e s
u
of
work
i
ngs
s ion of i mpo r tan t dev e lopm e n t s or by t h e blocking—
p
wh e r e unf avourabl e r e sul t s m i gh t b e ob ta in e d
Ou h i s pa r t t h e m i ne e xam i n e r mu s t b e car e ful no t to as sum e
an attit u d e of r e s t ra i n t a n d d i strus t toward s thos e conn e c te d w it h
th e manag e ment I n th e writer s e xp e r ie nce min e rs ar e a s
hon e st as mos t m e n ; a n d if t h ey som eti me s put th e b e s t si d e
befor e you it is mor e from a f ee l i ng of loyal ty to t h ei r e mploy e rs
t han a d el i bera te d e s i re to d e c ei v e Probably no t mor e than on e
i n a hun dre d woul d w i lfully m i sl ead you or u s e un lawful m e an s
t o e nr i ch your s ampl e s Bu t t h e hundr e dt h man i s g e n e rally
a cl e v e r rogu e a n d needs clo s e wa t ch i ng 5 a n d beca u s e of t h i s
on e man you mus t tak e no r i sks eit her i n t h e min e or i n th e
’
.
-
,
.
.
-
,
,
.
,
,
,
.
-
’
,
.
.
,
.
,
,
CH A P T ER I "
T HE
E " A M I NA T I O N A N D
M I N ES
—
E
N
T
N
T
s
z
O
C
V al uation
M
of
eta l
Con r n — Cl ifi ti o f O
Val tio o f A ll vi l Grou d
ce
ua
as s
s
ca
u
n
on
n
a
.
VA L U
A T I ON O F
.
M i nes — D e v el ope d M i n e s a n d G oi ng
in a M i ne— V al uatio n o f Coal Areas
re
.
payable ore in a vein or c oal in a s eam is manifestly a
certain fi n ite quantity 5 therefore the greatest c oa lfi e ld and largest
ore deposit must eventually see a day of exhaustion And if the
total quantity of ore or coal and the annual output are know n
the date of exhaustion is a matter of simple c al c ulation
A mining property bl e ssed with a good constitution — that is
e ndowed with a considerable quan t ity of valuabl e ore from the
dat e of discovery to th e point of e xhaustion — naturally passes
through th e successiv e stages of infancy youth full grown m a n
hood middle age old ag e and e xtinction
I nfancy is th e discov e ry stage of mine e xistence 5 youth th e
dev e lopmen t stage 5 full grown the payabl e going conc e rn in th e
meridian of lif e 5 middl e age the going concern past the meridian 5
old age the period of d e cad e nc e and exhaustion But all this is
tru e only of the mine that survives the early stages of e xistenc e
and l i ves what may be termed a full a n d pr ofitab l e life leaving
an honoured nam e behind
Som e min e s give promise of their later vigour ev e n in e arly
infancy a n d oth e rs tha t are weakly in i nfancy d e v e lop into a
robus t manhood T h e gr e at e st mortality t akes place in infancy and
youth S cores of promis i ng m i neral d i scov e ries ar e unabl e to sur
viv e th e stage of d e v e lopm e nt They n e ver becom e going conc e rns
But sud de n exhaustion is not an affection pecul i ar to th e v e ry
old or the very young mine Th e re ar e many notable e xampl e s of
v i gorous mines coming to a sudden e nd through exhaustion of the
ore reserv e s i n a way not e xpec te d or provided for by the
manag e m e n t
Th e m i ne e xam i ner will therefor e lik e t h e careful physic i an
T HE
‘
-
.
,
.
,
,
-
,
,
,
,
.
,
,
,
,
.
,
,
,
.
,
.
.
.
.
.
.
-
,
,
1 96
,
1 98
MININ G GEOLOGY
.
has bee n located by the prospector and a l e gal title obtained
for the ground forming what may be term ed a s urfa ce sh ow 5 or
that
h
b
t
e claim has b ee n pegged out on p osition alon e no vein
( )
or seam of valuable m i neral be i ng e xposed a t the surfac e
A S u rf a ce S h ow —I n th i s case th e outcrop has probably been
prosp e cted by trench e s and shallow shaft s su ff ic ie nt to disclose
t h e wid th d i rection of str i k e and d i p of the deposit
Hav i ng prov i d e d h i ms e lf w i th the best topographical and
g e olog i cal maps ob t a i nabl e the mine e xaminer will p ro c e e d w ith
h is exam i nat i on which will embrac e a considera ti on of th e
followi n g points
l e dg e
,
-
,
,
.
.
,
,
,
.
-
,
,
°
1
( )
2
( )
The g e olog i cal f e atur e s
The phys i cal f e a t ure s part i cularly with r e f e rence to t he
subs e quent work i ng of t h e proper ty s hould t h e r e sults
warrant this course 5 note such po i n t s as th e ba cks ava i l
—
—
i
able that s if the vein can be work e d wa t er fr ee 5 bu t
i f not m e nt i on i f sinking is l i kely to b e w e t or dry
m i n e t i mber and wat e r—power ava i lable etc
Sample the outcrop at di fferent points noting the width
of v ei n and p e cul i ar i ti e s of structure
Me ntion th e prox i mi ty or absence of valuabl e or worthless
min e s i n the dis trict
Make inquirie s as to past history of the fi e ld ob t aining
o ffi c ial stat i stics when possible
G a i n a p er son a l knowl e dge of th e local pe c uliar i t i es of the
o r e d e os it s in the n e ighbour i ng m i n e s
e
specially
noting
p
v e in structur e average width and value of or e accessory
m i n e rals country rock in fl u e n c e of di fferent kin ds of
country faults i ntrusive dykes meth ods of trea tmen t
mon thly output m i n i ng costs etc
.
,
,
,
,
,
,
-
.
,
3
( )
,
.
4
( )
,
,
.
5
( )
,
.
6
( )
,
-
,
,
-
,
,
,
,
,
,
°
,
.
,
When once 0 11 the groun d th e mine—exam i ner should make a
point of acqu i ring all th e gen e ral a n d part i cular informa ti on he
can ob t a i n for his future ref e r e nce and g u idanc e
Th e r e sults of th e sampling and obs e rvat i ons may b e satis
factory but the e xp e ri e nced min i ng e ngine e r will b e careful not
to comm it h i ms e lf to a de fi n it e opin i on as to th e potent i al valu e of
the prop e r ty upon surfac e in di ca t ions alon e Th e young e ngin ee r
“
must no t b e afrai d t o r e por t t o h i s pr i nc i pal s that t he d e v e lop
ment work i s in s u ffi c ie n t to e nable m e to form a de fin ite op i n i on
”
as to th e probabl e valu e of th e property
Th e e xp e rienced
engineer fi n ds no diffi c u lty in doing s o
Bear in mind that th e outcrops of silv e r l e ad z i nc a n d copp e r
lod e s ar e of te n less valuable than they ar e at some depth below the
surface 5 whil e those of gold are in many cases m or e valuable
,
.
,
.
.
.
,
,
,
.
T HE E
X A MIN A T I O N A N D
V
ALU AT I O N
OF M I
NES
1 99
.
Henc e w it h t h e former t h e j udgm e nt mus t b e gui de d mor e by
m i neralogi cal and geological cons i de ra ti ons t han by sampl in g
I f t h e ou t crop values a n d g e n e ral surround i ngs ar e sa tisfac tory
th e e xa m i n e r w ill i n most cas e s b e warran te d i n r e comm e nd i ng
f urth e r d e v e lopm e nt work b ei ng under ta k e n i n ord e r to op e n up
t h e ground for a f u ll e r exami nation Th e m i n e e xam i n e r from
his knowl e dg e of t h e groun d will b e abl e t o i n di ca te to h i s
principals th e na t ur e e x te n t and proba bl e cos t of s uch work
111 t h i s cas e it w i ll man i f e stly be to t h e i n t er es t of t h e i n te n d
ing purchasers t o acqu i r e a working op ti on ov e r th e prop e rt y for
a per i od of s ix nin e or t w e lve mon t hs or m a y be i f t h e work t o
b e unde r tak e n is consi derabl e t wo y e ars
Th e dee d of op tion s houl d b e l e gally e xecu te d be t we e n th e
int e res te d pa rt ies 5 cl ea rly s p e c ify t h e term of purchas e a n d s ta te
wh i ch part y is un de r obl i ga ti on t o pay ren ts tax es royal ty and
comply with t h e labo u r r e gulations e tc dur i ng t h e curr e ncy of
t h e op ti on
The v e n dor may som eti m e s r e qu i re an im m e dia te ca s h payment
of an agr e ed sum of mon e y on th e e xecut i on of th e d ee d of op t ion
such sum t o be cons i de r e d par t of t h e purchas e mon e y s houl d th e
prope rt y be tak e n ov e r ; or h e may cov e nant that a c e rtain
i
n
m
i
n
e
d
e
velopm
e
n
t
eit
h
e
r
monthly
or
s e c ifi e d s u m be spent
p
dur i ng t h e whole p e r i o d of t h e op ti on a s a guarante e tha t t h e
work w i ll b e pros e cu te d w it h v i gour
It should be r e memb e r e d how e v e r tha t t h e engin ee r for t h e
purchas e r i s g e neral ly t h e bes t j udg e as to wha t sum shoul d b e
s p e n t i n t he d e v e lopm e n t work n e c e ssary t o e nabl e h i m t o form a
r e liabl e opinion of t he value of th e propert y O u th e o t h e r hand
t h e chanc e of do i ng good bus i n e s s shoul d no t b e lost by pursu i ng
a n i ggardly pol i cy w i th t he v e ndors Th e refor e e ach case mus t
b e j udg e d on its own m e r it s
S o far we hav e a ssumed tha t t h e surface ou t crops gav e
t o warran t furt h e r de v e lopm e n t be i ng und e r
s u ffi c ie n t values
tak e n w it h a v ie w of op e n i ng up t h e groun d for a more cr iti cal
e xam i nat i on According t o t h e c on fi g u ra t io n of th e s urfac e a n d
pos iti on of t h e ou t crops t h e or e v e in w i ll b e prosp e c te d by lev els
“
—
—
t
on
along
t
h
e
cours
e
of
t
h
e
or
e
body or by
dri v e n
n
d
e
e
cross c u t s and l e v e l s t h e r e from or by a shaf t or s haf ts
I n s e l e c ti ng th e s ite s for t h e afor e sa i d l e v e ls or shaf ts i t i s i n
mos t cas e s a dvisabl e t o k ee p i n m i n d t h e poss ib i li ty of th e s e works
b ein g u ti li s ed i n th e p e rman e n t work i ng of t h e m i n e should t h e
r e sul t s j us t ify t h i s cours e
Aga i n th e surfac e ou t crops may be wor t h l e ss a n d t h e prosp e c ts
in s u ffi c ie n t t o warran t any expe n dit ur e on prosp e ct i ng
O n t he
o t h e r han d t he valu e of t he prop e r ty m ay b e so obvious tha t th e
,
,
.
,
-
,
.
,
,
,
,
.
,
,
,
,
,
.
,
,
,
.
,
,
,
.
,
-
-
,
,
.
,
,
,
.
.
,
.
.
-
,
.
,
.
-
.
,
,
.
,
.
,
2 00
MININ G GEOLOGY
.
m i ne examiner is j u s tifi e d i n r e comm e nding th e imm e diate
purchas e I n this cas e no prospe c ting should b e unde r tak e n by
th e e xamin e r until a fi r m Op tion of p u r ch a se has b e en acquir e d on
b e d rock t erms
Und e veloped properties of such obvious valu e are rare and
h e nc e e xtrem e cau ti on must be ex e rc i se d by th e e xaminer before
recomm e n ding an i mm e diate purchase L edg e s of silver l e ad ore
and gossans of pyri ti c or e bodies hav e be e n d i scov e red in s i tuations
t hat left littl e room for doubt as to th e ir gr e at valu e e v e n from sur
face sampl i ng and examination 5 and th e sam e h a s proved t ru e of not
a few valuable deposits of magnetite sp e cular iron and manganes e
Bu t e ven if the exam i ner have the immediate purchase of the
property in h i s mind h e will seldom hav e much diffi c u lty in
obta i n i ng the right (under an opt i on of purchas e ) to sp e nd a
mon t h or two in sampling a n d surv ey i ng preparato ry to the
completion of the purchas e
P egg ed on P os ition —This is generally an un de v e lop e d property
often possess i ng no surface ind i cations of valuabl e ore or mineral
I t is how e ver not on all fours with th e cases we have already
d i scuss e d I n som e cases position means e verything 5 in othe rs
nothing F or exampl e an ar e a surrounded by working coal m i nes
iron mines or oil wells occurring in the same formation in the
-
.
-
.
,
-
.
-
,
,
,
.
,
°
.
.
,
.
-
,
,
,
.
~
,
.
,
-
-
,
,
FI G
’
.
74
.
—S ectio n
o f Val ble Bedded D po it
ua
e
s
.
absence of faults or igneous dykes is an area already proved
valuable by its j uxtaposition to valuable mines Or a cla i m
p e gg e d out on the strik e of a lode that has proved to be payable
up to the boundary i s a potentially valuabl e property O r a
claim pegg e d out on the d i p of a fi a t lying lod e seam or b e d that
has been proved to be valuable by th e outcrop m i nes i s a prope rt y
in the absence of great faults igneous dyk e s or a change of rock
formation that may prov e to be of great value
I n the above fig u re A is an ou t crop cla i m assumed to b e
,
.
.
-
,
,
,
,
,
,
.
,
2 02
MININ G GEOLOGY
.
Particulars of ve i n outcrops prosp e c t ing work don e
7
Values obta i n e d from sampl i ng
(
8
D
( ) i scuss i on of general surroun di ngs
9
O
( ) pinion as to futur e prospects a n d r e comm e nda tions
Thr ee cours e s may b e pursu e d accord i ng to th e circumstances
the property may b e
6
( )
-
,
.
.
.
.
,
,
Rej
e
cted
( )
b
S
e
cur
e
d
on
working
option
( )
P urchas e d
a
.
.
.
I f th e e ng i n ee r r e commen ds t hat an opt i on b e s e cur e d he
should g i v e full d e tails of th e charact e r and ext e nt of the proposed
work i t s probabl e cost time r e quired for th e work its e ffe c t wh e n
complet e d and proposed method of supervision
—
D e v e l o p e d M in e s a n d G o ing C o n c e rn s
Th e commercial
valuation of a m i n i ng prop e rt y in th i s sta g e is based upon t h e
following cons i derations
,
,
,
,
.
.
1
( )
Th e quant i ty
and
valu e of
be ing d ev elop e d
n e t p rofit per ton
or e
de e
or e
and quan t ity of
.
Th e
3
Th
e
annual
ou
t
put
to
yield
a
)
(
certa i n cap ital i sation
4
The
probable
l
i
f
e
of
min
e
)
(
2
( )
Op ed,
.
n et
p
rofi t
per cent
0 11
.
a
.
.
Th e quant ity of or e that m i ght b e expected to b e Op e ne d up by
furth e r d ev e lopment work mus t not b e los t s i gh t oi But t h e
quantity a n d valu e of such or e are unknown quanti ti es and th e
i mpor tance t o b e at tach e d to th e m i n calculat i ng th e mine val u e
must in e v e ry cas e b e d e t e rm i n e d by th e charact e r of t he
ore bo dy a n d the value of the or e alrea dy d e v e loped and won
I n all cas e s the fundamental basis of m i ne valuation is the ne t
.
,
-
.
t
fi in
o
r
p
s ig h t
.
Som e ve i ns are notoriously patchy wh i l e others are e qually
consis te nt as m e tal produc e rs 5 hence 11 0 saf e rul e can b e laid down
as t o th e prosp e ct i v e valu e of un de velope d ground Th e local
cond iti ons mus t gov e rn e ach cas e I t is how e ver well for t h e
engineer t o r e m e mb e r that th e ore values of ve i n deposi t s are
mor e li able to sudd e n var i ation than thos e of b e dded de pos i ts
As i n th e former cas e s th e min e e xam i ner will proceed t o th e
ground e qu i pp e d w i th th e best topographical and geological
maps obtainable ; also offi c ia l reports a n d statisti cs if any are
ava i labl e
When onc e 0 11 th e groun d t he e xam i ner will fin d it a dv a n
t a g e ou s t o pursue t he follow i ng course of proc e dur e al though i t
,
-
.
,
.
-
,
-
.
-
,
,
.
,
,
T HE E
X A MIN A T I O N
A N D V
ALU AT I O N
0
must b e clearly und e rstood t hat c i rcums tanc e s alter cases The
suggestions g i ven h e re are general ra th e r t han special and must
b e m odifi e d to su it th e n ee ds of each case
.
,
( )
a
Car e fully exam i ne th e mine plan G e t t he min e manager
to e xplain th e general scop e a n d ext e n t of t h e un dergroun d
workings
E xamine t he surface ou tc rops (ii any ) a n d no te the
geolog i cal and phys i cal fea tur e s
E xamin e th e boundary l i nes and car e fully no te t h ei r pos iti on
w it h r e sp e c t t o th e dip a n d cours e of t h e v ei n or e body
or s e am b e ing work e d i n t h e m i n e
N ote the r e la ti on of th e u n de rg nou n d work i ngs t o th e
surface boundar ie s
Hav e a look at t h e or e coming to t h e surfac e also a t t h e
rock on th e d u m p
E xam i ne and mak e a not e of t h e surfac e e qu i pm e n t i nclud
i ng mills and all m e tallurg i cal plant a n d appl i anc e s
When d e s cr i b i ng s te am e ng i n e s g i v e t h e numb e r a n d
size of cylind e rs maker s name pressure of steam carri ed
by boiler e t c
-
.
.
b
( )
,
.
( )
c
-
,
-
.
d
( )
.
()
e
,
.
(f )
,
.
-
,
’
,
,
,
.
Th e fi rs t da y or t wo is spent in get t ing your bearings and
becom i ng ac qua i n t ed wi t h th e manag e r a n d no ti ng wha t mann e r
of a man he i s A f e w da ys occup i ed on t h e surfac e i n pr e
l i m i nary work i s g e nerally t ime w e ll sp e n t M ak e a not e of any
fac t s presented or o ffer e d to you D o not no te O p i n i ons and 0 11
your side b e car e ful to o ffe r none
,
.
.
,
.
.
E
xamin
e
t
h
e
u
n
d
erground
work
i
ngs
accompan
ie
d
by
th
e
(g )
m i n e manager or his d e puty According to t he e x t en t of
t he workings it may tak e a day 0 1 t wo to do t h i s
Aga
i
n
e
xam
i
ne
t
h
e
m
i
n
e
plans
Y
ou
w
i
ll
b
e
able
t
o
follow
1
1
( )
t h e m i n te llig e n tly fr om th e informat i on you have ga i n e d
.
°
,
.
.
undergroun d
.
Y ou have now rea ch e d the cri ti cal stag e i n your e xamina ti on
You have nex t to d ete rm i n e th e con diti on of t h e m i n e ; a n d
among th e qu e s ti on s tha t w i ll na t urally com e i n to your m i n d w i ll
be t h e follow i ng
u r e ahead of it ?
I
s
t
h
i
s
a
young
m
i
n
e
w
i
th
a
prosp
e
rous
fu
t
1
( )
I
s thi s a young m i n e doom e d t o e arly e xhaus ti on ?
2
( )
Has
t
h
i
s
min
e
r
e
a ched i ts max i mum po i n t of pr od uction ?
3
( )
?
I
s
t
h
i
s
an
old
m
i
n
e
approach
i
ng
e
xhaus
ti
on
4
( )
I
s t his an old mine with th e e y es p ic ke d ou t ?
5
( )
The answer to these questions is to be found in th e quan tity
.
MININ G GEOLOGY
2 04
.
valu e of ore in s i ght D o not forget that in a vigorous w ell
manag e d m i n e the d evelopmen t work w i ll be commonly two years
ah e ad of the m i ll
an d
,
.
.
underground with your own a ss is ta n t and sk etch out
your sch e me of sampling
Sample the min e in a systemat i c manner This may take
a week or s e veral weeks ac c ording to th e magnitude
of the workings and siz e of ore bodies
The
g
e
neral
(
princ i ples of m i ne sampling are described in the chapt e r
treating of M in e —sampling and O re
Complete your surface invest i gations G e t min e returns of
output of ore an d values e xtracte d or of min e ral shipp e d
or exported min i ng and milling costs etc
Carefully
verify doubtful po i n t s
Before leaving th e district make as c ompl e te an exam i na
ti on of the neighbouring mines as circumstances will
p e rmit noting character of country ore bodies being
worked general characteristics of said or e outpu t
returns methods of treatment costs of mining a n d
m i lling
G
o
,
.
.
,
-
.
-
.
,
.
,
,
.
-
,
,
,
,
,
,
,
.
Ou
no account allow yourself to be hurried in your examination
Tak e your own time
Cultivate a deliberate temperament
Base your est i mates on facts but be sure of your facts 5 a nd in
your report be car e ful to differentiate between facts and opinions
Y our next care is the assay of your mine sampl es and in this
you must be gui ded by local considerations I f you are a skilful
assayer it is pr e ferable for you to hir e an as say ofiice for a day or
two supply your own fl u x e s crucibles etc and perform your own
assays 5 or your assistant will probably be able to do so for you
I n whatever way the work of assaying is done it is imperat i ve
th at the results must be accurate and reliable
.
.
.
,
.
,
.
,
,
,
,
.
,
.
,
.
m
( )
Plot your assay values on tra c ings of mine plans and th e n
consid e r th e results
-
,
.
The form of your report will d e pend upon your
t i ons M an i festly th e prop e rty may b e
r e com m e n
da
.
1
( )
2
( )
3
( )
R e j ect e d
S e cur e d on option
Purchased a t onc e
.
.
.
in your Opin i on t h e property should be rej ected it w i ll b e
unnecessary to furn i sh elaborate details conce rn ing it B u t i f
I f,
,
,
.
MININ G GEOLOG Y
2 06
.
in mo r e or l e ss rectangular blocks of limited size exposed
by workings on all s i d e s Th e y are only applied to or e that can
be e xtracted and treated at a pr ofi t
Th e phras e or e in s ig h t i s amb i guous and may m e an ore e xposed
I t may thus be misl e ading and should
0 11 o n e two or more s i des
th e r e for e be allow e d to fall into disus e
A simpl e and clearly de fi n e d c las s ifi c a tion of ore is as follows
i
r e D e ve lop ed — Blocks of ore exposed on four sides
O
()
—
r
t
e
e
ii
r
e
P
a
l
D
e
v
l
o
d
Blocks
of
ore
e
xposed
on
three
or
O
p
y
( )
two sid e s
iii
O
r e E xp e cte d to be D e ve lop e d — Blocks of ore that may be
( )
r e asonably expected to exist beyond or below t he last
v i s i ble or e E xposed on one sid e
1
Philip Argall cons i de rs that th e thr ee phrases or e—develozyed ore
being dev e lop ed and ore e xp ec ta n t should cov e r all t h e estimates
a mining e ngineer i s called upon to make
I n th e cas e of a v e in expose d by surfac e ou t crops only ther e
is no ore in sight notwithstanding that the valu e s may b e high
ta in e d
.
.
,
,
.
,
,
.
.
.
.
.
'
.
.
.
,
,
.
,
.
,
FI G
76 —
.
.
L ongitu dinal
S
e tion
c
on
Co r e o f L o de
u s
.
t h e l e tt e rs a b e
a n d cl
r e pr e s e nt promin e nt outcrops on th e cours e of a lode
The hollows between t hes e outcrops ar e assum e d to b e obscur e d
by ov e rburde n A numb e r of sampl e s s e lect e d at each ou t crop
show e d th e pr e sence of valuabl e or e M an i f e s tly any e stimat e of
th e quanti ty of payabl e or e woul d b e m or e gu e sswork
Ther e i s noth i ng t o show tha t th e payabl e or e i s con ti nuous
b e tw ee n t he di ff e r e n t ou t crops I t may or may not b e s o Again
th e payable or e a t the d i ff e r e n t ou t crops may b e m e r e loca l
patch e s or the t runca te d r e ma i ns of a pay shoo t that may have
b ee n of considerabl e d i m e n s i ons pr i or t o th e later sculp t ur i ng o f
t h e country
T A R i k rd T h S mp lin g
d E tim ti
f O in M i
p 80
N w Y ork 1 90 4
in On e D tm ens zon — I
'
Or e exp os ed
.
n
fig
.
76
,
,
,
.
.
.
.
,
.
-
,
°
.
1
.
e
c
.
,
a
,
.
e
a
an
s
a
on
o
re
a
n e,
.
,
T 1I 11 E
X AM IN AT I O N A N D
V
ALU A T I O N
or M I
N ES
2 07
.
I n th e above e xampl e we have t h e proof of th e fi rs t p rin cip le
i n accordance wi th wh i ch a n or e body e xp os e d in on e dimen sion
a ff o rds no basis for th e e stima ti on or e in s ig h t
O re exp osed in T wo D ime ns i ona — We w i ll n o w assum e t ha t
surfac e e xcavat i ons hav e proved t h e con t inuanc e of th e pay shoo t
from poin t s a to 0 fig 7 7 and tha t a shaf t has b e en sunk on t h e
v e in at po i n t 6 to a d e pth of 60 f ee t
,
-
.
-
.
,
,
.
FI
G
—L
.
o git di
n
nal
u
S
e tio n o f L ode
c
.
Th e shaf t su n k at b e xposes t wo s i des or dim e ns i ons of th e
t riangles of ore a b e and c b e for a thickn e s s e qual to t h e w i dth
of t h e breast of or e e xpo sed in t h e shaf t
ft 6
ft
Let a
and b e = 60 ft a n d t h e m e an
wi dth or th i ckn e ss of pay or e = 4 ft Assum i ng t ha t t h e payabl e
valu e s c on t inued to t h e bot tom of t h e shaf t w e hav e t wo t r i angl e s
of or e par t ly d e velop e d
F rom th e above w e ge t the m i n i ng e ng i n e er s s e cond pr i nc i pl e
.
.
,
.
,
.
,
-
.
,
.
’
,
T h a t a n o r e body exp ose d in two d im ens ion s g iv es a tri a ng le of or e
only p a r tly de vel op e d
—
r
i
F
e
S
os
o
n
ou
d
s
I n t his e xampl e a l e v e l has b ee n
e
d
Or e exp
driv e n on th e cours e of th e v ei n , a n d a r i s e pu t up from po i nt f t o
th e surfac e , a n d ano th e r ris e from 2 t o n Th e do tt ed l i n e 3 n 771
s hows t h e lim it s of the pay shoo t on t h e w e s t s i d e of t h e shaf t
Th e or e de ve lop ed now i nclud e s th e r e c tangul ar block Z) 6 f c Th e
i rr e g u lar block b s m e is e xpos e d on thr ee s i d e s , a n d th e r e for e
con ta i ns or e no t ful ly d evelop e d Th e r e l i anc e t o b e placed upon
est i mat e s of valu e in t his block w i ll d e p e n d upon th e charac te r
Th e capac ity of th e s e
is t ic s of the ore body a n d loca l con diti on s
-
.
.
.
.
-
.
.
.
-
.
°
or e bodies can eas i ly b e c alcula te d for any g i v e n wi dth
F rom the above w e g et th e th i rd pr i nc i pl e T h a t a n
-
.
,
exp ose d
in
de vel op ed
f
o
f
a
om
°
dime n sion s
known
i
v
e
s
g
app r oxi m a te
a
r e c ta n g u la r
m ea n wid th
a r ea
a nd v a l ue
.
o re- body
’
f
o
or e
2 08
MININ G GEOLOGY
.
I t is manifest that three d i mensions do no t fu lly expos e a
rectangula r body of ore I f in t he abov e e xampl e we take sid e s
6 e e f and f e as th e known dim e nsions t hen t h e value of the
.
,
,
,
triangle b k c is an unknown quantity Again if e b b e and e f
are th e known dim e nsions t hen th e t riangle of or e e h f is
unknown
,
.
,
,
,
.
FI
G
78
.
.
L ongitu dinal S e ctio n
-
o f L o de
.
I n working mines with the d e velopment well in advan c e of th e
mill the lev e ls and rises by means of which the ore is cut up into
r e ctang u lar blocks for stoping a ffo rd four dimensions or sides for
e xamination and sa mpling
O nly in exc e ptional c ases should the length of a block ex c eed
twice th e h e ight The smaller the blocks the more trustwo rthy
,
,
.
.
will be the estimates of
de velop ed
—This is found
or e
.
by div i ding the number
of cubic f e et of sol i d or e contain e d in the block by the number
of cubic fe e t of solid ore in a ton The number of cubic feet in a
ton of ore depends on the specific gravity of th e or e and varies
from 1 2 to 1 5 cubic fe e t for a ton of 2 0 00 lbs
I n m e asuring up ground which is f u lly d e veloped allowance must
b e mad e for faults dykes probabl e h or s es of rock and pillars of or e
that will nev e r b e tak e n out A d eduction of 10 per c e nt will
b e s u ffi c ie n t in most cas e s 5 but obviously no e mp i rical rule can
be laid down Th e c haracter of the ore body and contain i ng rock
and lo c al experience will a ff ord the safest gu i des to follow
—
—
I
n
e
es
rv
e
s
many
cases
the
m
i
ne
e xaminer may
P r o ba bl e Or R e
be j u s tifi e d in assuming that the payable ore e xt e nds above 0 1
below the working faces or open gr ound I n this matte r he must
exerc ise great caution His only guide is the general metalliferous
E stima tion
f
o
T onn a g e
.
.
,
.
,
,
.
.
-
.
,
,
.
.
°
.
.
.
2 10
MININ G GEOLOGY
.
I n the maj ority of cases t he e xaminer s r e port will d e al with
’
the following points
1
ituation
and
means
of
access
S
( )
2
Area
title
owners
r
e
nts
or
royalty
et
c
( )
3
G
eological
structur
e
illustrat
e
d
wi
t
h
cross
s
e
c
t
ions
( )
4
Phys
i
cal
fea
t
ur
e
s
with
r
e
f
e
renc
e
to
for
e
s
t
s
ra
i
nfall
wat
e
r
( )
pow e rs etc
5
oa l fi e ld
Th
e
area
of
Th
i
s
should
b
e
shown
on
a
colour
e
d
c
( )
(
plan )
6) Thickness of seams and pr e senc e of ston e —par t ings
7 ) E xistenc e of faul t s and dyk e s
Probable
tonnag
e
of
coal
8
fi
r e c la
pr
e
s
e
nc
e
of
and
irons
t
one
5
( )
y
d
Quality
of
coal
I
s
it
har
and
strong
or
soft
and
friabl
e
9
?
( )
G ive an alys e s of coal state wh e th e r it i s us e ful for st e am
household gas sm e lting e tc purpos e s D iscuss pro
po rtion of sulphur pr e s e nt water ash et c
fi
S
e ld lies so as to b e wat e r fre e
1
0
tate
i
f
any
portion
of
th
e
( )
and if s o what ar e a
—
G
iv
e
probable
cos
t
of
min
e
d
e
v
e
lopm
e
nt
11
( )
2
Cost
of
su
r
fac
e
equipment
1
( )
3
State
probable
cos
t
of
produc
t
ion
1
( )
State
situation
of
mark
et
for
coal
access
and
probabl
e
14
( )
cost of transport of sam e
1
5
D
iscuss
e
xtent
of
market
probabl
e
competition
et
c
( )
r o fi t p e r ton
tate
the
probable
n
et
16
S
( )
p
I n an a r e a in wh i ch the quant i ty of coal i s d e duced from surfac e
outcrops and a f e w borehol e s it i s a ne e dless r e fin e m e n t to at te mpt
to calculate t h e quant i ty of coal with math e mat i cal e xactn e ss
Having determin e d th e approx i mat e ar e a and t h i ckn e ss of coal
and made du e allowanc e for brok e n coal along outcrop faults
and dykes th e quantity of coal that can b e e xtract e d may be
c al c ul ated on the following bas i s
T o n s p e r A cre
F or e v e ry foot of brown coal
10 0 0
p i tch coal
1 10 0
b i t u m i nous coal
12 00
cann e l coal
1300
anthracit e
15 00
Seams of c oal a n d beds of shal e ar e sampl e d in th e sam e way as a
v e in — that is by cu tt ing a narrow groove from roof t o fl o or a t r i gh t
angl e s to the plan e of t h e d i p Surfac e outcrops should b e dr e ss e d
down with a p i ck before th e sample is broken as ou t crop coal is
often wat e rlogg e d 5 and som eti m e s t he cracks ar e fi lle d with fi n e
sedim e nt or sand carried over t he exposure by running water or rain
.
,
,
,
,
.
-
,
.
,
,
,
,
.
.
.
,
.
.
.
.
,
,
,
,
.
,
,
.
,
,
,
.
-
,
,
,
.
.
.
.
,
.
,
.
,
.
.
,
,
,
,
.
,
,
,
,
,
,
.
,
.
T HE E
XA MIN AT I O N AN D
VAL U AT I ON
or
V
AL U AT I O N
A LL UV I A L G
0 11 MI
RO U N D
NES
2 11
.
.
Th e val u at i on of alluvial or placer depos its e ither for dr e dging
or hydraul ic sl ui cing i s a ff ec t ed by dete rm i ning th e amou n t of
gol d con taine d i n a m e asur e d quan tity of mater i al ob ta i n e d from
sh a f t s or boreholes placed a t reg ular i nterv als i n th e ar e a under
con s i de ration
—
k
a
T h e Wor of S mp lzn g
Fi rs t su r v ey the block of ground a n d
plot it on pap e r to a larg e sca l e — say 2 chains to th e inch for
areas b et w ee n 5 0 and 10 0 acr es and 1 cha in to the in ch for areas
und e r 5 0 a cr e s
D ivi de th e ground on t h e plan in to bloc ks of 1 to 5 or 6 acr e s
Th e shape of t h e blocks w i ll d ep e nd on t h e surface con tours
t h e di r e c ti on of th e dr a i nag e and t h e probabl e direction of th e
gol d leads
I n som e cas e s t h e ground i s a long narrow s t r i p s i t ua t ed on one
or bo th s i de s of a riv e r 5 in o t hers te rrac e lands i n a vall e y wh i ch
ar e i n many cases in te rs e c te d by la t eral str e a m s
M ak e a mark i n t h e c e n t r e of e ach block and th e n number t h e
blocks in cons e cu ti v e o rd e r Proc ee d to t h e groun d and put a
s tak e or flag i n th e c e ntr e of e ach bloc k Th e s e s takes mark t he
s it e s of t h e sampling hol e s
Th e dep t h of grav e l may vary from no t h i ng to 40 fee t or mor e i n
v e ry dee p groun d
Wher e th e groun d is dry and no t d e e p i t i s cus tomary to sink
hol e s or shaf ts a t t h e s e l e c t e d po ints Th e whole of t h e ma te rial
e xcava t ed from t h e hol e is car e fully measured i n a box of kno wn
capac ity w a shed by cra dl ing the gold con ten ts w ei ghed and t h e
results r e c o rded
Th e reco rd of each hole emb ra ces informa t ion on th e following
po i n ts
1
D
e
p
t
h
of
ground
( )
—
l
2
Character
of
bott
m
t
ha
t
is
wh
e
th
e
r
slate
or
f
se b o t tom
o
a
( )
Charac
t
er
of
grav
e
ls
note
pa
3
rtic ul arly if b e d s of clay large
( )
(
bould e rs or drif t ti mb er ex i s t in ground )
2
r
d
s
0
i
Quant
it
y
of
mat
e
r
al
excavated
i
n
cubic
yar
s
plu
e
4
p
( )
c en t ( all t h e boul d ers bo t h small and gr eat must be in
cluded i n t h e measur e m e n t )
5
( ) Quan t i ty of gol d ob ta i ned
6
Quan
ti
ty
of
gold
per
cubic
ya
rd
( )
I n ground wh e r e t h e si n king of hol e s woul d b e impe d ed to a ny
inch or 6 i nch
cons i d erabl e e xte n t by wa ter it i s usual to pu t down 5—
bor e hol es at t h e s e lected poin ts Th e holes ar e l i ned w it h tubing
a n d th e
ma teri al ex t racted by t he san d p u m p c oll e cted in a
wood e n t rough w a shed a n d t he gol d conten ts w ei ghed
,
,
.
’
,
.
,
,
.
.
,
,
-
.
,
,
.
,
.
.
.
,
.
.
,
,
,
.
.
,
.
,
,
.
,
.
,
,
.
.
.
-
,
-
,
.
,
,
,
.
2 12
MININ G GEOLOGY
.
Re c ord the depth of the hole a n d calcula t e th e cub i c cont e nts
from the outside diameter of t he p i pe plus 2 0 per c ent The
excess is add e d because experience has shown that the gold values
cal c ulat e d from the di splacement of the pipe alone ar e always
higher than t he actual r e turns This is no doub t larg e ly due t o
the c i rcumstance t hat a h i gher e xtraction or saving of the gold is
e ffe cted in th e sampl i ng t ests than i n actual pract i c e
Wr ong M e th ods of S a mp ling — The method of s e l e cting the test
samples from open fac e s or from the sides or fl oor of small
streams has often l e d to erroneous conclusions I n th e se places
th e gold is generally mor e or less concentrated thus render i ng it
impossible for th e examiner to form an approximate estimate of
the average value of the gravels
Pannings taken from t he to e of gr avel faces and from water
cou rs e s cut through th e gr avels are in t eresting but infer e nc e s
drawn from the gold ob t ained are usually v e ry misleading
F urthermore it must not be inf erre d that a plac e r claim whi ch
r eturns good
wag e s to a small party of working mates w i ll
necessarily pay dividends to a company working on a larg e scal e
Working on a small scale the m i n e rs are always on the track of
t h e g old I f the lea d is lost the fact is known at once 5 but work
ing on a large scale where the shifting of quan t ity is an impo rtant
factor in order to insur e adequate retu r ns for the capital invested
ri c h and poor g ravels al i k e are moved th e reby reducing the
gen e ral average
Cal cu la ting the A v er a g e Va lua — Th e average value per cubic
yard is found by multiplying the numb e r of gr ains of gold per
cubi c yard found in each hole by the depth of the hole in feet
and dividing the sum of these produ c t s by the sum of the dep t h
in feet as follows
,
.
,
.
,
,
.
.
,
.
,
.
,
.
.
,
,
,
,
.
,
,
D epth o f Hole
in
F eet
.
Gra i n s
e
r
p
o f G ol d
C bi Y rd
u
c
a
.
3
1 1 0 3 113
3
I N DE"
G E S o f geol ogi l time 4
A ll v ial depo it m pli g d l
tio n f 2 1 1—2 13
Al m 1 4 2 1 4 3
A l m i i m 14 4
A l m h ale 1 4 2 1 43
A l ite 1 4 2 1 4 3
A am or ph i m 6 8
A ata e 91
A de ite m i er l fo u d i 6 7 ;
f 1 12
ffi iti
7 ; prop y liti atio
A
ca
u
u
,
u
s
.
,
s,
un
n
.
s
s
n
a
.
,
,
,
n
v a ua
.
,
n u
an
.
,
u
n
s , sa
s
o
.
,
.
,
.
,
n
s
s,
n
e s,
n,
n
a s
,
n o
s
,
,
f
l ignite
A nth ra ite g
29 5
ged to by ba al t 30
h
A ntim o n ite 1 44
A nti m ony 1 4 4
Ap tite 1 77
Arge tite o rren e f 4 2 1 80 5 i
l o de 5 4
Ar eni c 1 4 4 1 4 5
Ar e opyrite i
vein 6 1 1 4 4
1 4 5 5 m i er l a o iated with 8 4
A be to 1 4 5
A ph al tum 1 4 5 14 6
A gite a prod t o f o ntact meta
m orp h i m 1 2 7
c
an
c
e
a
,
.
.
,
n
s,
,
n
,
.
,
s n
n or e
,
a s
n
s,
ss
s,
,
c
,
,
.
.
s
,
,
u
o
.
,
s
c
ccu
,
s
.
,
.
,
a
,
s
,
,
s
o
.
uc
,
s
c
.
,
.
e
i e
eg o
i o epo
Bo z
o t o o
Bo
Bo i
o ite o
o e
i
e
o
i e pi g
o i eo i
B
e
B lu carm n , 1 73
B lu
r u n d, 1 5 4
B og - r n d
s s, 22
n a n a s , 7 1 , 72
B ra e f s da, d
s s of 2 5
,
rax , de osits of, 2 5 , 3 7, 1 4 7
r c a c i 1 2 3, 14 7
B rn
c c u rr n c of, 42 , 5 8
,
B s s s, 5 5 m n ral s f u nd in , 6
B ras s s in c al , 30
B r n s r n s a s nd ca rs f sal , 7 0
Br m d
f s l v r , ccu rr nc of, 4 4
u n ch s , 7 1
A LK S
30
,
B ket
an
.
o e of o
m d
,
c cu
rrence
33,
B ry te 1 4 6 1 47
B l t affi ity f 7
xite 1 4 2 1 4 3 1 44
B
B e he 71
Biotite h a ge f 91
Bi m th 14 7
Bit me S A ph lt m
1 66
B l k b nd
Ble de i ont t depo it 3 9 12 7 5
at Broken Hi ll 4 4 5 t B kto
52 5 i
ga h vei
45 5 i
vei 6 1 5 verti l di trib tio f
7 6 5 m i er l a o iated with 8 4 5
o rce o f zi 1 85
th mai
a
s,
a sa
n
,
au
,
u
s
-
ac
n
o
.
,
.
a
s
ee
.
or e ,
a
,
.
,
n
,
n
u
.
,
.
c
,
o
,
s,
nc
.
,
u
.
s
ac
n c
e
s
ca
n
a s
n s u
,
ss
n,
uc
ns,
s
n s,
s,
a
,
n
.
n
u
n
c
,
nc ,
.
ore
o
,
it
.
.
epo it
.
.
e e
e
o
.
.
.
i i to o
e o
e e
t
.
.
C A I N O Z O I C period 4
C i r gorm a o iated With pp h i re
.
,
n
a
22
ss c
,
sa
s,
.
Cal mi ne 1 85
C l ite verti al di trib tio f 7 6 5
q rtz p e dom orph f 91
C m brian g 4
Carbon a o iation o f prod ti ve ore
with 8 3
Carbon diox i de 1 15 1 2 1 1 34
C rbonation o f mineral 6 8
C rboni fero g 4
Ca iterite S T i n tone
C t y a oc iated with pph ire
a
.
,
a c
c
,
ua
s
a
s o
e,
ss
,
n
u
s u
a
o
,
,
.
.
c
uc
s
.
,
,
,
.
,
a
s,
a
us a
a
o f,
.
.
ss
B
.
’
22
.
ee
.
s
.
ss
e,
s e
e,
sa
s,
.
Cell l o e ab orption o f opper
u
80
s
s
,
by ,
c
.
Cem ent 1 4 7 14 8
Cem e t pla er w ith g old 1 6 1 7
C em e t tion belt f 6 8
Cer ite o rren e f 43 4 4
C h l opy rite o rren e f 4 4 4 6
vei 6 1 5 verti l di
58 5 i
t ib ti
f 7 5 5 mineral a o i t d
with 8 4
C h ly be te pri g
i di tor o f
ir o 7 0
Ch i tol ite a prod t o f onta t
m etam or ph i m 1 2 7
C h im ey h oot 7 1
,
,
n
.
c
n a
u ss
s
o
,
c cu
,
a c
u
on o
a
,
c
o
ns,
.
,
,
,
ca
s
,
n
s
n,
s
ss c a e
s
as
n
ca
s
.
as
uc
,
s
n
,
.
,
a
o
cc u
,
n ore
r
.
,
c
.
,
,
-
s
s,
,
.
.
c
c
I N D E"
Chl o ride o f ilver o ur e e f 5 8
C hl ori t e min er l o iated with 84
C h romi te m in eral a o iated with
8 4 5 in peri dotite 1 0 8 1 30 5 i
erpentine 1 0 8 1 4 8 5
f 1 49
C hro mi m 1 48 1 4 9
C h ry l ite 1 4 5
Ci n bar m in eral a o iated with
8 4 5 depo it
f 117 1 18 1 19
C la ti ro k S S edim e t
C l y ab o rptive po wer f for metal
7 9 8 0 5 fo rm ation f 7 9 5 petro
le m ab o r bed by 8 0
G oal
origin f 2 7—2 9 5 m ode o f
o c rre c e 2 9 5 g f 2 9 5 effe t
prod ed i
by
dy ke
30 5
v rietie f 32 ; t
i fo rma
tion f 32 33 ; w orl prod tion
s
r nc
cc
,
a s ass
,
,
u
ss c
,
so
n
a
.
ss
s
,
c
c
s o
s
n s
ee
.
o
u
s
o
n
s
o f,
e
a
,
c s
o
o
s,
s a
,
,
n
es
’
,
uc
s
1 49
a
a
s,
s a
o f,
2 0 9, 2 1 0
of, 2 9 5
ul
u
,
s
o f,
2 9, 3 0
al , 1 4 9, 1 5 0
.
fa ti n g
.
Cob t
C obalt ore m i eral
84 5 o
rren e f
Cob l ti e 1 4 9
ccu
a
n
c
o
o iated with
c
15 0
,
Col e m a n nite , 14 7
ds ,
o ll
w r o f,
C oi
s a ss
,
.
po e
.
to ab orb
m
s
etal
s,
.
,
.
,
c
s,
s
-
s
u
,
o
s
s o
.
c
o
.
,
,
s,
s
o
s
,
s
,
,
a
,
s
c
s,
a
c
s
s
,
s
,
,
a
s,
r c
,
u
.
,
e
s,
cu
c
s
s,
o
s,
o
ue
ce
o
.
,
o
,
o re
Co e
C eta eo g 4
Cr h zo e 4 2
Cry ol ite 1 4 3 1 5 2
C llin an di m ond 1 5 8
C prite o r ence f 38
.
.
e,
n
us
,
,
u
.
.
,
a
.
.
,
‘
u
,
cc u r
o
,
,
.
7 2 , 7 3 , 8 1 , 8 2 , 1 3 4 , 135
u rs s , 7 1
us a
,
,
cc
,
s,
.
ore
c
,
.
c
s,
,
-
o
u
r
,
s,
v
,
-
,
c
,
u
e
.
,
a
,
.
s,
,
,
.
D eep min i g
s o
Denudati on 2 3
Dev on ian a g e 4
D i a base affi n ities o f 7
D iam o n d placers 2 1 1 5 7
Diam onds ass oc iated With sa pp hires
2 2 5 at Ki m berl ey 38 5 K im berley
diam o nd m in es 1 53 1 5 5 5 parent
roc k 1 5 5 1 5 6 5 genes i s of 15 6 5
1 5 7 5 larges t
in do leri te
158 5
,
.
,
,
.
,
.
,
.
,
,
.
,
,
,
,
,
-
,
,
,
,
,
,
pply f 1 5 8
D io rite ffi iti f 7
Dip o f trata 2 6 2 7
Dip f ul t 98
D olerite di m ond i 1 5 7
D ow th row 96 1 00
D y b lo wi g pl
18
Dy ke 5 5 m i neral fo d
eff e t prod d by 30
su
o
.
,
n
a
,
s
.
.
n
n,
s
a
,
,
.
.
,
n
-
,
,
s,
a
r
es o
,
ace ls
.
,
uce
c s
in ,
un
s
2
,
.
ogite 15 6
f
i
e ent di t b ti
earth r t 10 7
rren e f 4 3 1 80
Em bo l ite o
rren e f 6 2
E rgite o
E o ene g
4
Equise tum s in C arbo i ferou
Ec l
El m
.
,
'
s,
s c us
c
o
th e
n
,
.
,
ccu
o
c
ccu
e,
a
on
n u
s
,
,
o
c
,
.
.
,
.
n
28
6 5
.
,
E A R T H evolution o f t h e
na
C o m b tru tur e 6 7
C o ngl o m erates 3
Conta t depo it 38 4 6 1 2 4—1 2 7
C onta c t m et m orp h i m 12 4 —12 7
Copper occ rren e f 34 35 38 5
ore f in ontact depos it 4 0 ;
ore f in ein 70 5 abs orption f
by c ell l o e 8 0 5 in
erpentine
1 0 9 1 30 5
tc
o urc e nd pro
d c tion f 1 5 0 1 5 2
Copper gl n e in onta t depo it
39 5 in l od e 5 8
in
toc k works 38 5 in
Copper
l od e
5 3 5 7 5 8 ; in erpe n ti ne
n d oth er
o k 7 2 7 3 5 pseudo
m o rp h o s after w ood 8 3
C opp r py rite oc rren ce f 3 8 4 5 5
in o nta c t depo it 39 1 2 7
C opro lite o u rrence f 3 6
f
C o untry in fl n
vein
n
c
old 1 4 15 1 6
it f 88 8 9
wi h g
n , lim
,
.
s
t
a ds
’
.
,
e
,
.
n
s,
D EEP l
s,
.
C o l areas val ation
C o l e m po itio n
80
,
n,
a
o
,
,
,
uc
0
.
.
,
,
.
,
o
u
,
,
,
,
c
c
s
,
.
,
.
s
s
u se s o
,
,
a
n
,
,
,
.
,
,
s
.
,
c
s
,
o
2 15
.
s
ag e ,
.
oc rren e
ontac t dep it 39
Ex el io r diam o nd 1 5 8
E m b esc ite
cu
,
s,
os
c
c
o f,
c
s
in
38 5
.
.
,
F A H L B A N D S 9 46 4 7 82 12 7
F h l e occ urren e f 4 2
Fa l t in c oal eam 2 9 30 5 exte n t
f 3 0 5 alo ng vein
7 2 5 d fi n it i n
f 93 1 0 4
93 94 5 dyn m i
Fel pa r h an ge f to kao l i 5 8 5 to
topaz 1 8 4
Fern geo l ogi cal devel op m ent f 2 8
F ir ec lay 15 8
or
a
o
o
.
,
s,
s
.
,
,
c
,
s,
u
,
,
,
,
s
cs o
a
,
c
,
o
o
e
s,
,
,
,
.
,
n,
,
.
,
o
s,
,
.
.
,
Flin tie s , 8 3
Fl a r , 6 7
Fluca n , 7 2
Flu r ( fi u or s ar) 1 5 9
F l ds in c a l , 3 1 , 32
F r s s f ar n f r u s a g e , 2 8
.
o te
.
.
o ite
-
p
.
,
o
o
o e t o C bo i e o
.
.
G A L E N A in c ontac t depo its 3 9 1 2 7 5
at Broken Hill 44 5 at B u c kto n
5 2 5 in o re
4 5 5 in gas h vein s
vein s 6 1 5 vertica l di str ibu ti on o f
7 6 5 minera l s ass oc iate d with 8 4 5
p seu dom orp h s of a fter wood 1 1 6
s
,
,
,
,
,
,
,
,
,
,
,
.
I ND E "
2 16
G arn ets
as soc iated with g ol d 1 8 ;
minerals as s o c iated with 8 4 5 a
pro du ct o f c o n ta ct m etam orp h is m
,
,
,
,
12 7
Garn ierite 173
G aws 30 31
G eo l ogi c al ti m e
,
,
.
.
,
,
.
,
period
2 5
,
,
4
.
G ol d form s o f al luvial 18 5 as so c i a tes
o f allu vi al 1 8 5 origin o f al lu vi al
18 1 9 5 p rec ipitates of 19 2 0 5 in
th e R a n d b a n ket reefs 3 3 3 4 5 in
T readwell m i n es 37 38 5 in c o nta c t
depo s its 4 0 ; in s a ddle reefs 4 9
5 1 5 in l o des 5 3—5 7 5 in vei n s 7 0 5
,
,
,
,
,
,
,
,
,
,
,
,
,
s of ,
,
,
,
.
,
Iron h a t 6 9
I ron ore in l imestone 73
Iron p y rite s in c ontact depo sits 39
4 1 4 3 1 2 7 5 n ea r gran ite 4 1 5 at
B roken Hil l 44 5 in fahl bands 4 6 5
in l o des 5 6 5 7 5 in ore vein s 6 1 ;
verti cal di s tribu tion o f 75 76
o x i dation of 7 8 5m in eral s a ss oc i ated
with 8 4 5 o ccu rrenc e of in fi s sure s
o f basalt 1 1 7 5 in m etam orph ic
ro ck s 1 2 7 5 gold reduc ed by 1 41
Iro n ston e b l o ws 6 9
,
.
,
.
,
,
,
,
,
,
,
,
.
,
.
,
-
,
,
,
,
bo z 72 5 i l y 7 9 5
i di ator bed f 82 8 3 5 m i er l
a o iated with 8 4 5 i ande it
11 4
1 15 ;
1 35 ;
water
i
d y iel d f
o r e prod tio
1 5 9—1 6 1 5 am pl i g
d val atio
o f all vi l depo it o nt i i g
in
n a n as ,
n
c
ss
c
s
or,
u c s,
,
,
n
a s
e s,
s
°
n
sea
uc
n,
,
an
n
s
u
c a
n
,
,
s
n
a
o
an
s
n
u
a n n
c
s
,
,
2 1 1 —2 1 3
.
G ol d
n
r n
s,
ss n ,
7
n
n,
ore
s
for matio n
1, 2 9 5
and u s s
ag e
,
0
o re
u c s
e
e
e t og i o
p
epo it
e
fault
of
H em tite
a
in
,
1 6 6 , 16 7
fau l
a
of,
165
of,
.
n
n
.
s s,
s
o
e
urc s
.
o e
epo it
,
s
s
of ,
a
,
.
.
uc
S
Ke rargy rite
ee
30 , 6 7 , 6 8
n
n
n ac
c
.
,
.
.
,
,
,
.
.
,
,
.
118 ,
ge f 91
I m preg tio 9 4 7—48
I di ator bed 82 83 1 6 0
I o dyrite o c rren e f 43 4 4
Iro o r e d pro d tio f
o
ns,
s,
c
,
Lepi do den dro n s
ren ce of
3 2 , 33
3
,
L i m esto n e
L i m o n ite
.
epo it
de e di g water
cu
n , s u c s an
.
,
.
,
d
c
o
L o des
s
s
n
.
r ters
ch a ac
,
uc
,
n o
,
1 66
2 3,
o f,
2 4,
by
1 66 ,
i t
53 58 5 w d h
,
o f , 6 3,
6 4 ; l n h o f , 64, 65 5
s r
o f,
6 5 5 dip o f, 6 5 , 6 6 5
h , 6 6 ; arra n m n
d
f ma r
in , 66 , 6 7 ; r c v ry f l s , 101
t ike
ept
28
-
e gt
ge e t o
tte
eo e o ot
C rbo n i ferou
in
a
s
ag e ,
.
Pl to i ro k
egreg tio o f ore
S ee
.
s
c
u
a
—1 33
n c
c
s
n
.
s,
10 6
.
g e ite 169
g etite i bea h nd 1 2
a o iated W th g ol d 1 8 5 with ti
2 0 5 in o nt t depo it
39 5
m i neral
s o i ated with
84 5
r e e f i m gm
107 ; a
Ma
Ma
n s
n
.
,
n
,
sa
,
n
ac
a s c
o
s,
,
c
s
cu r n c
c
1
o re ,
.
formed
o f,
s,
ss c
.
,
,
16 7
c u
.
,
n
ag e ,
o e of o c r
29 5 m d
of ,
ag e
,
G
g ti
,
Carboni fero u s
in
.
M A MAS
Ma ma
.
,
na
.
L y c opo di u m s
68
7 9, 1 1 1 ,
ra s ,
su
ch an
40
,
.
.
.
.
104
.
tion o f m i e l
l p h i de
oge
16 8
.
,
,
sc
I G N E OU S ro c k s S ee Plu ton i c ro c k s
I lmenite asso c iated with ti n sto n e
n
.
,
L ig n ite
.
93, 94
l d s, 5 7 ; d
,
s
H orn sil v e r
20 ;
.
,
,
s,
a
H
o
L A N D origi n o f s u rfa ce features o f 2
L a teral secretio n th eory of 1 34—1 41
Laurenti an a g e 4
Lava 5 5 m i n era l s fo und in 6
Lead ores o c curren c e o f 36 5 in
l o des
53 5
in l i m estone
73 5
s o urc es a n d
y iel d o f 1 6 8
L eader 75
L ead zi n c ores in c o nta c t depo s its
28
He ve o f t 99 100
Hor ble de
prod t o f o t t
m et m or ph i m 1 2 7
H y dra
y dr
i
.
,
.
Hor e
.
,
.
a
Kt op i
-
G rav l s , 3
G r a M u l d am nd, 1 58
G y s um , d
s s o f , 2 5 , 36 5
a n d u s s o f, 1 6 5 , 1 6 6
HAD E
.
,
on
ca
c as s
KA O L N , 1 5 8
a am r h s m , 6 8
Ke ra rgy rite , 1 5 4
Koh -i-n or d a m nd, 1 5 8
,
.
,
.
raph ite
30 5
.
,
I
.
,
.
,
o f,
,
nu
,
,
,
ac
a
o
c
n
n o
G
n
s c
4
ag e,
,
ore e o dary enri h ment f
i zo e o f weath e i g 77 5 dim i
tio f with depth 81 8 2
G ol d p l er 1 0 —1 9 1 5 9 1 6 0
G o a 69
Gr n ite ti
i
6 5 l
ifi t i
s,
JU RA S S I C
s
,
n
a
as ,
s,
cc
2 18
I ND E "
Po ket 7 1
Pot bl ow 30 3 1
Prim ry period 4
P e dom orph i m o f m ineral 8 9 91
P ilom ela e depo it f 2 3 2 4 1 6 9
Py rite S Iron pyrite
Pyrol ite depo its f 2 3 2 4 1 6 9
Pyro xe e m ineral a o iated with
s,
c
.
-
s,
.
,
a
,
s u
.
s
s
n
s,
s
,
,
ee
.
us
s
o
84
h
y
174,
.
P rr otite o
,
c cu
.
,
c
rren c e of
o e
.
,
,
ss
s
,
.
,
,
s
,
n
,
,
4 5 , 4 6 , 1 73,
verti cal
ineral s
eta
1 75 5 in l d s , 5 7 ;
r
u
o f,
76 5 m
c
d w h , 8 4 5 in m
h c
c s, 12 7
i t ib tion
a o iate
it
m o r p i ro k
d
s o
.
,
s
ss
.
a gangue o f mi neral s 5 9
6 6 6 7 ; verti cal di strib u tion o f
75 5 ab sorption o f o x i de o f i ro n
by p u lveru lent 80 5 m in eral s a s
s oc ia t e d with 8 4 5 p s eu do m orp h o u s
after calc ite a n d orth oc las e 91 5
depo s its o f c hal c edo n i c 1 13 1 1 4
QU A R TZ
,
as
,
,
,
,
,
,
,
,
1 15
,
,
.
Quartzite 3
Qu i c k s i lver
,
,
G
.
timu us formation f 3 5 e rth
r t hi cfly form ed f 3 5 al tera
tion f 3
S erpenti ne m i eral a o iated with
c
o
c us
c
o
s
,
.
,
n
,
84
a
,
o
’
s
ss c
,
.
ke o
e
i e ite
ii
epo itio
b o pti e po e o ge ti o
p eie
pe o op
te oo
i i
i e o
e e
b
oe
ei
i e to e
o e
ie
i e e oe
o t t epo it
o e
ie
te
i ke i e
ip
tite
o t i
tio
po
i e
epo it
pe
io
o t t epo it
p o t o egio
et o p i
epo it
S ha n c al , 3 0 , 31
S h al s , 3
S d r , 1 66
S l ca , d
s
ns of, 77 1 1 1- 1 1 7 5
a s r v w rs f la n u s a nd
u lv r s d , 80 5
s u d m r h o f,
af r w d, 1 1 6
S lur an a g e , 4
S lv r , c c u rr nc of, 3 5 , 3 6, 4 4 5 in
fah l ands , 46 5 r s o f, in v ns ,
7 0 5 in l m s n , 73 5 in clay , 7 9 5
s u rc s a n d
y ld o f, 1 8 0 , 1 8 1
S lv r l ad r s , in c n ac d
s s,
40 5 s urc s a n d y l d of, 1 81
S la s , 3, 1 8 1 , 1 82
S l c ns d s , 7 2
S l s, 2 9
S mal
14 9
S l fa a r c ac
n ; e Hec ts of, in r
du c in g m n ral d
s s , 1 1 1—1 2 3
S
c u lar
r n , in c n a c
d
s s,
39, 1 2 7 5 a
r duc f r nal
m am r h sm , 1 2 7 5 d
s s of,
.
.
.
.
.
.
-
.
.
.
.
.
.
s
o ur e
c s an d
e ti
ie
y ld o f, 1 80
.
i t ib tio
R EA L A R , v r ca l d s r u
n of,
76
R c n ag e , 4
R dru h
c c u rr n c of, 4 2
,
R
n d am nd, 15 8
R v rs d fau l s , 94
Rhy l
a ffi n itie s o f, 7
,
R d r, 6 7
R c s,
m ra u r o f , 8 5 , 8 8
s,
Ru
ass c a d w h g d, 1 8 5
w h sa
h r s, 2 2
R u y la c rs , 2 1 , 2 2
Ru l , s u d m r h u s f rm s o f, 91
.
ee t
e t ite o
e e
ege t i o
ee e
t
o ite
i e
o k te pe t e
bie
o i te
it ol
it pp i e
b p e
ti e p e o o p o o
.
.
.
.
.
.
.
.
.
.
.
p
e r ry l ite ,
1 79
.
pi e
o i te it ol
tep
t
t b te e ti
i t ib tio
to k o k
t ike o t t
t ike
t
p i e o oppe
C opper
pyrite
S l ph i de o f l e d
G le
S
S l p h i de o f i lver
Arge tite
S
S l p h i de o f zi n
S
B lende
S ul ph i de
pre ipit nt o f g old 1 9
78 8 3 1 4 1 ; verti al di tribu tio n
f 75 7 6 7 7 7 8 7 9 5 o x i datio
f
7 8 5 fo rm tio n f 1 1 4 1 4 1 5 in
il i eou inter 1 2 1 5 i er ptive
ro k 130
S l p h r depo it
f 2 5 2 6 37 1 11
S n l , as s c a d w h g d, 1 8
S
fau l s , 2 9, 30 , 100
S i ni , v r cal d s r u
n o f, 7 6
S c w r s , 9, 3 7, 3 8
S r
f s ra a , 2 6
S r
fa u l s , 95 , 97
S ul h d
f c
r
S ee
.
.
.
.
-
.
.
s
.
u
a
u
S A D D L E -B A C K S , 30
r fs , 42 , 45 , 4 9, 5 0, 1 60 ,
S addl
161
S al , d
s s of, 2 5
”
f m n s , 1 94, 1 95
S al n
S am l n , m h ds f ore , 1 8 6—1 96
S an ds , 3
S ands n s , 3
lac rs , 2 2
Sa h r
a r du c f c n ac m a
S ca l
,
m r h sm , 12 7
184
S ch l
,
S ch s s , 3
S as , r na n o f, 2
r d, 4
S c ndary
S d m n s , firs t 0 1 1g i11 o f, 2 5 c on
.
e ee
.
t epo it
ti g o i e
p i g et o o
.
.
.
.
to e
pp i e p e
po ite p o
op i
ee ite
it
e o igi tio
eo
pe io
e i e t
.
.
to
.
.
.
°
o t t et
.
s
c
o
c
,
,
c
c
u
s,
u
1 1 7,
su l
s
n o
o
s s
,
,
,
a
s
s
a
,
.
.
c
,
.
n
ee
.
,
,
na
a
ee
.
u
s,
ee
.
,
,
,
s,
n
u
,
,
.
s o
s
,
1 1 8,
1 19,
ph retted
u
,
,
12 0,
o e
h y dr g n
7 0 5 s u rc s
o
e
12 3,
as
12 4 ,
a n in
e
dic at or o f,
a nd
yi ld
of, 1 8 2
S u l h u r d x d , 111 , 1 2 3
S u l h ur c ac d , f rma
n 0
S we llie s , 30 , 31
Sy n
a fi nitie s of, 7
,
p
p
e ite
.
io i e
i i o
tio
.
.
.
I ND E "
of
g ol d
o ur en e
cc
,
r
o f,
c
19
.
o igi o
I
o
,
e
po e i
.
e
ie
tio
t
o e
2 0 5 in l d s
cc
of,
,
4 7,
72 ,
84 5
p e do morp h o after orth o l e
1 30
131
90 5 i er pti e ro k
1 32 5 o r e
d y ield f 1 8 3 1 8 4
21 5 i
T itanifero us iro n in a d
us,
s u
n
s
u
c as
v
c
s,
u c s an
,
o
s
n
,
,
,
,
.
n
s,
ei
ei
ei
e
o t op
o it o o et i
po itio o o te t
o e e t
eo
e t
e t
it ept
o e o ot
o o to
-
te t
8 5—8 8
g
eg eg te
ite
po
et o p i
WA N T
30
,
u
,
m
ineral a o iated with
s
ss
c
o
ac
,
,
-
,
,
e
,
,
o
n
,
s o
.
,
s
Z
Z
Z
A N D CO
nc
o
.
c
a
,
c
s
e,
o
s
s,
a
ca
n
,
.
,
.
o
e
y ield f 1 85
inc i lim e to e 7 3
ir on a o iated with g old 1 8
l N o, s u rc s a n d
ore
c
.
,
,
L TD
n
c
.
,
c
,
,
uc
,
,
c a e
ss
cc u
.
u
NE I L L
s
,
1 40 5
13 9,
1 10
12 3,
b lt f 6 8
Wol fram m i eral a o i t d with
8 4 1 84 1 85 5 o
rre e f 1 73
Wo lla t nite a prod t o f onta t
metam o rp h i m 1 2 7
W od a pre ipit nt o f g ol d 1 9 5 o f
h o rn il ver 8 3 5 o f opper o re 8 3 5
p dom o rph o f g le a after
116 5
d f il i after 1 1 6
W l fenit 1 72
,
an
B Y
,
sc
se u
D
.
,
s
TE
o t t
r
o
R IN
to
-
n
sc n
s
P
.
Water tion f 2 3 1 36
w h en de e di g 2 2 2 4 1 3 7
1 4 0 5 at h igh tem pe ature
1 2 3 5 w h en a end ing
12 2
,
,
.
.
,
o rmal ine
.
,
Wea t h e 1i n g
T
it e
n
f c av i s in , 6 0 ; a ge
VE NS , r
f fill in g o f, 6 1 63 5 u c r s o f,
68 , 6 9 5 c nd i n f m a ll c c o n
n s of, 70 ; s n f c n n s ,
7 1 5 w a l l m v m n s o f, 7 2 5 s c n d
a ry
nri c hm n of, 7 7—80 5 im
v r sh m n
of , w h
h , 80
d
f l s , 1 0 1—10 4 5
82 5 r c v ry
h eo r s
f f rm a i n o f, 12 9—1 39 5
val u a n o f, 1 92 , 1 93
V n s , fis s ul e , 9, 5 2 —5 8 , 1 1 2
V ns , as h , 9, 5 1 , 5 2
V n s , s r a d , 9, 4 8 , 5 1
V su vian
and
r duc
f c n ac
,
m a m r h s m 12 7
s
o
n
ss c
E D IN B U R GH
,
.
,
.
,
.
.