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"~~~{~li ... .: ;:',
AN ECONOMIC STUDY
OF THE PROPERTY OF THE
TIDE WATER TRAP ROCK C011PANY
AT
BRANFORD,
COl'n~.
IRVING E. ADAMS.
":~,
I ~
I
.
INTRODUCTION.
Oonsidering
Valley
the wealth of triassic trap in the Connecticut
and the proxinity of Boston and NewYork markets
remarkable,
to the superf'icinl
observer,
that
so li ttle
sally
recognized fact that
the best
of road material,
.es t and toughest
ing;
and 1t is
to water
the univer-
are,
at the
the greatest
sane time,
difficulties
and the deposits
transportation
themselves
1;hnt economic
furnish
the hard-
in crush-
only when the condi t t ons of' deposi tion
cially favorable
The rea-
the more banic igneous rocks
they
and offer
Notwithstanding
seems
stone
has been quarried in the past for use a.s a road metal.
son, however, 1s easily discovered.
it
are espe-
easily accessible
exploi tation
is,
as a
ruf,e , possible.
Now it so happens
that
tho Connecticut
crosses the state as a series of boldly
Valley
outcropping
1n every case but one to quite reach
ridges,
fails
board.
This makes resort to railroad
trap,
which
north-south
the sea-
transportation
necesGa.ry;
and, since freight rates are high, and the New York, New Haven,
&: Hartford Railroad Company are themselves
is
slight opportuni ty for the independent
at a profit.
Moreover,
large
quar-ry-owner-
the net~by Palisades
to very recent times, adequately
The eastern main trap ridge
shippers, there
deposits
to mine
have, up
supplied the New York n~rket.
does,
however,
Sound; and the Tide Water Trap Rock Company
extend to the
controls its south-
ernmost portion.
liar! ties,
This ridge possesses
certain geological
which, aside from their high theoretical
greatly reduoe the difficulties
peou-
interest,
of mining and crushing
the rook.
These considera.tions, coupled with the fact that the Palisades
deposits are no longer available
future possibilities
as a source of supply, make the
of this ridge, as a road-metal
producer
enormous.
This report will deal with some problems
property
as a future economic
degree of development,
etc.--details
factor.
financial
Details
geological
problem.
tory tests, \v111 be incorporated,
the utility ot the various
FinallYt
report,--
The causa of the extremely
low
since it is at bot-
The physical properties
trom an elaborate
of the rock, as determined
con~any,
to a stockholders'
crushing price will be dealt with at length,
tom an interesting
this
of plant, present
status of operating
belonging essentially
will not be here touched upon.
involving
series of labora-
together vlith a discussion
tests, based on collateral
the cause of the abnonnally
of
reading.
high r-ecemen t atn on value
will be considered.
LOCATION.
As noted above, the property in question
1s located about
six miles east ot New Haven, in the town of Branford,
ly outcropping
beginning
ridge of trap, locally known as "Pond Rock", and,
one and one-eighth
road embankment
and easterly
on a bold-
(1 l/S) miles
across Lake Saltonstall,
direction
for six miles.
o
8-10 -E
extends
of the rail-
in a northerly
The property
oomprises
some fifty-five
companying
acres, distributed
(55)
as indicated
on the ac-
blue print.
Sections
ftc" and
flD" on the blue
print lie entirely on the
ridge.! the general diroction of which is shown by the contour
lines.
At one point, UN", the underlying
a short distanoe.
The quarry
tical face sixty feet (60t)
stretoh
of' low land;
crushing plant.
sohistose
it
high.
for
a ver-
Section "B" represents
a
includes the Company bud Ldd.ngs and
to be later utilized
pany has an option
overlaps
front is at "X", presenting
Section "A" represents
rook,
sandstone
some island property
for storage bins.
on
The Com-
I'G".
on section
GENERA!, GEOTA>GY.
The mode of origin and condition
assio strata
of deposition
along the Atlantic border is a muoh mooted question
among geologists.
of the material
A wholly
theory
adequate
explaining
forming the sandstone, varying
the finest sand to the coarsest conglomerate,
mixed; the peculiar
lenticular
such a continual adjustment
plicated
of the tri-
structural
never been presented.
1;11esource
as it does from
indiscriminatingly
shape of the deposits,
requiring
to sea. leve-l cond1 tions; and the cora-
relations
of the accompanying
As pertinent
"trap", have
to the subject in hand, we
are alone concerned \vi th the question
of the origin of the trap.
The formation has been studied in great detail
in the Con-
necticut Valley by several able men, wld the facts of structure,
as now exposed, worked up very carefully.
Nevertheless,
interpretation
difference
of these facts the greatest
in the
of opinion
--1-
still prevails.
As to whether
series of nearly parallel
consolidation
the trap was erupted
fissures in the strata,
and subsequent
disturbancen;
sents a series of volcanic lavas ejected
"through a
and after ther
or whether
it repre-
before the tilting ot
the strata took place, is still an open question.
It so ~appens that "Pond Rockff,at the southern
the quarry is located, possesses
connection,
since, according
peculiar
0.
end of ~lich
interest in this
to Prof. Davis,
it affords
the key
to the solution of the origin of' all the trap ridges ,of the Valley.
According
to the latter authority,
Pond Rock represents
overflow sheet, the arSl~ents advanced being briefly
smmned up
as folloV1S: the base exhibi ts Ii ttle metamorphic action;
back or upper surface is charactorized
texture;
highly
its structure
is brecciated
altered and hydrated.
Mr.
has contended
the
by a decided amyGdaloid
a.nd irregular;
:r~. O.
in a later. and, for this particular
an
Hovey,
the rock is
on the other hand,
area, more detailed work,
that, in the main, these features might obtain if
the rock was intrusive
considers positive
in origin;
w1d further
eVidence in the invariably
advances vnlat he
somewhat higher
dip of the over~ying sandstone.
Since the conclusions
structural re·lations
hannonious,
reached by these writers,
based on
as eXhibited over extended areas are so in-
it seemed to me that a careful
itself in a. very restricted
study of the "trap"
area, and from as many points of
view as possible, might serve to throw some light on this puzzling problem.
For if the structural
evidence
is inadequatet
the rock itself should present some features that would indicate
its "intrusive"
or "extrusive"mode
of origin.
Further, it ap-
pealed
to rne that too little labora.tory work accompanied
the re-
ports of these writers.
GEOT..OGY OF POND ROCK.
Pond Rock ridge is not continuous
throuGhout.
ExtenGive
faulting divides it naturally into three members.
The southern-
most, and the one to be considered in detail, possesses
al trend
Cf
of about N-14 -VI, and is three-fourths
long, tenminating
just north of the Branford
(3/4)
turnpiRe.
southern end rises abruptly above the older paleozoics,
n gener-
of a mile
The
from
which it is separated by a stretch of marsh land, to a height of
140' above mean low tide.
we proceed north,
until,
It diminishes
at 1t s tenninat1on,
30', while the latter is only Got.
the eastern gentle.
in height and width as
Sandstone
the former reaches
The western slope is steep,
flanks both slopes.
The top of the ridge presents a peculiar
appearance.
The surface soil is' extremely
being qUite generally exposed.
and ch~racteristic
thin, the bare trap
It 1s quite universally
weather-
ed out as small, angular fragments,
tough and undecomposed
cept along the weathered
.An examination
surfaces.
these fragments reveals the presence of numerous
ex-
of one of
steam vesicles,
sometimes empty, sometimes filled with secondary calcite or
quartz.
Nowhere do these vesicles penetrate
than a fraction of an inch.
elongate,
rock.
and resemble
to a depth of morc
Quito often these vesicles are
more the etohings of acid on a limey
Boulders ot sandstone abound along the eastern slope, but
no true outcrops were observed.; hence it was very difficult
asoertain
the dip of the overlying
an exposure
search
~
the railroad
just
south of
The soft, rather sandy shale hore exposed
agreed in charaoter with the boulders
slope.
By dint of hard
in p Lace was noted
undoubtedly
cnt.
sandstone.
to
The contaot
had a general
strewn along the eastern
trend
of N-71o -E,
and dipped
to the east at an angle of 74~.
Several contacts
as you proceed
difficult
north
of trap and underlying
along
the steep
western
sandstone
slope.
to Imow when you have a true contact,
of trap are often engulfed in the sandstone.
age dip of 60 E, a somewhat higher
tained by Hovey.
generally
figure
The strike is I~16°-E.
indurated
are noted
It 1s often
sinoe boulders
I obtained an
aV8l"-
than the one asoerThe sandstone is quite
to a depth of 2'-3', it being otherwise
a ~oose, shaly texture.
of
Conglofiler1tic phases were noted at 1n-
tervals.
The quarry opening is at the extreme
ing
a vertical
This structure
point of view, highly
the mass is remarkable
is peouliar,
important.
for its homogeneity.
stony gray color. finely crystalline
very intricately
veined
affording relief
to an otherwise
unique
ophitic
end, present-
faoe 60' high, and clearly revealing
ture of the trap.
mercial
southern
,vith a \vhitish
among most diabase
structure
and from a oo~
Oonsidered
as a unit
Of a rather dark,
and very dense in texture,
mineral,
mostly
sombre surface--it
traps of the vicinity.
is visible
the struc-
to the naked eye.
calcite--
stands
No trace ot
The ve1nlets
caloite vary from a mere thread to a dianleter of 1/4", and
of
r,mu-
fy through the rook in every conceivable
the mass, as it were, into numberless
direction.
small blocks)
apart readily in the process of crushing~
however.
being remarkably
An examination
hand lense reveals
They. divide
which fall
the blocks
themselves,
hard and tough.
of one of these fragments
the presence
a black mineral,
mostly
whits feldspar.
Its microscopic
of abundant
with the a.id of a
shapeless
augite, with numerous
structure
masses
of
tiny flecks of a
will be discussed
in
detail later.
Along the sides
evidenced
decomposition
places has progressed
composition
by
decomposition
shows considerable
sta.ins of iron oxide, and in some
enough to yield a muddy red soil.
has followed the veining,
mentsbe1ng still
preserved
of the opening the trap
solid trap.
the interior of the frag-
Consider.ad as a ~hole,
has not progressed
fart
clear to the grass roots.
have not, on the whole, much affected
The de-
however,
the main mass being well
Alteration
and hydration
the crystalline
structure
theory of structure
from the
of the rock.
C01ICIJJSIO}TS.
To deduce a wholly competent
above observed
al relations
another
facts, is,ta
are 'too cbseure ,
standpoint.
mind, impossible.
my
if/emust approach
Petrographic
evidence
The struoturthe problem
should help decide
the mode of origin of the rock, and the conclusions
such study be correlated
from
derived from
with the field observations.
I see little evidence
to warrant
an extrusive
mode of ori-
sin for Pond Rook.
As stated before, there is comparatively
little alteration and hydration of the constituent minerals; the
amygdaloidal texture is restricted to a very superficial layer
along the'back
or upper surface, and this might
just as well ob-
tain in the case of an intrusive sheet it the overlying
was fria.ble or iInperfectly
consolidated;
sediment
there is an entire lack
of flow structure; induration of adjacent sediments is not restric1;ed to the under surface;
the texture
is homogeneous throu81
out, neither true breccia (except in a few contact specimens)
nor vi treous variations
being noted;
quarry opening had been available
I think if' the present
for Prof. Davis' observation
not so much stress wou ld have been laid on some points of his
argument.
Neither does the rock resemble in the sligh~est degree such
~vdoubted
dykes as F~st and West rocks.
The coarse ophit1c struc-
ture of these dykes is not duplicated here, nor are the latter's
variations
in texture
from centre
to contact
here present.
More-
o*er, suoh structural evidence as we have available clearly prohibits
such a mode of origin.
then, Pond Rook to repres~nt
I conoe1ve~
ilmnense intrusive sheet.
deformation.
pressure,
The intrusion antedated
all important
The rock cooled rather rapidly and under moderate
producing
porous nature
the remnants of an
the finely crystalline
of the adjacent
of a thin,vesioular
layer.
sandstone
texture.
permitted
Accompanying
the formation
the later 'folding,
which raised the :mass to its present oblique position,
tensive faulting.
trend separated
Two parallel faults With a general
the lower member
The rather
was exl~~SE
of Pond Rock fron! the remainder
of the ridge.
The stresses
induced in this faulted bloakresul1r
1Dt trom the strain to WhiCh it was sUbjected, produced incipwhich later became
ient fractures
soluble
resulting
constituents
by atmospheric
ohannels
for the deposition
from the weathering
of
of the rock
influences.
Thus' Nature's. processes have served not only to bring this
01' material
va~luable mass
which permit inexpensive
time, producing
to sea level, but to induce condi tions
quarrying, and Without,
properties
detrimental
rook as a road material.
consideration
at the same
to the behavior
This last assertion
of its physical properties
of the
1s verified
as determined
by a
by labor-
atory teS~t to which we Will now turn our attention.
rABORATORY TESTS.
There seems to be a differenoe
many engineers
selection
regarding
best adapted to a
Local oonditions
alone must deoide
particular
admit that the most aocurate
ue of a material
local1 ty.
and method
I'ieverthelesst all Will
and rapid dotermination
of the valhave
and these results
cor-
on actual wear.
to be used as road metal must possess
It must be hard, tough, and durable;
ad for use on macadam roads,
erties; moreover,
play an important
the material
in the laboratory,
related with observations
characteristics.
tests in the
is effected when the physical properties
been carefu11ystud1ed
All material
in the minds of
the value of laboratory
of road material.
role, and experience
of opinion
its du.st must possess
it is desirable
that a smooth
certain
if 1nten~
binding
prop-
surface be main-
-10-
ta1ned, yet one that is not too hard, or slippery,
must. further, be free from dust and dirt.
or noisy.
All laboratory
a1m to throw all possible light on the probability
It
tests
of the mate-
rial at hand fulfilling these conditions.
These tests may be conveniently
grouped under the following
heads:Specifio Gravity.
Abrasive Res1stanue.
Cementation Value.
Reoementation
Value.
Absorptive
Power.
Weathering
Testse
Percussive
"
Compressive
Strength.
Ohem1'calAnalysis.
Mineralogical
Analysis.
SpecifiC Gravitl_
Prom many points of view a detenm1nat1on
ity is ot considerable importance
rial.
in the seleotion
To a oertain ext'ent it influences
great importance
of high
Spa
in estimating
Branford
ot road mateand is of
Moreover,
a rock
gr. is less liable to have its finer detritus
remov-
eralogic composition
An
durability,
covering power.
ed by the action of Wind or rain.
the crushing
of specific grav-
It depends primarily
and compactness
of the rock.
strength increases with the
average of four determination
trap yielded 2.82.
Spa
on min-
In general
gr.
made with samples of the
A very normal result for a diabase
-11...
Abrasive Resistanoe.
-Aside from the mechanioal
disintegration
by
of' roadstone
the expansive foroe' of frozen ,vater, a much' more important
for the wear of roads is the abrasion
by'traffic,
and the value
of a roadstone largoly depends on its resistance
sion.
Without going into detail, these various
cause
to this abraprocesnes
may be
summed up as follows:-
briefly
I.
Wear and tear of travel.
Aotion of horsestfeet.
(a)
(b)
(e)
II.
ii
"
'Wheels.
due to Y,eight of vehicle.
Pressure
Wear produoed by natural
forces.
(al Heavy rains.
(b)
Winds.
(c)
Chemical disintegration.
Cd)
Excessive
(e)
Frost.
Various
temperature
changes ,
machines have been devised
to irnitatet as nearly as
possible, the action of these forces~ but all are, necessarily,
imperfect.
Toughness,
the important
cohesiveness,
factors controlling, abrasive
as a factor does not enter here.
the influenoe
and chemical
Hardnasa
To attain a 'fair estimate
Further, the custom of employing
ried saJJ1plesfor this test is to be decried
to the action of solutions
of
such tests unreliable.
freshly
since continual
quar-
ex-
of deoomposing organic matter
on the road surface rapidly weakens
making
resistance.
are
of these several factors by a single test is obvi-
ously difficult.
posure
durability
the bonds
of cohesiveness,
-12-
The machines
ple.
A weighed
employed are quite alike in princi-
heretofore
a definite number
quantity of rock is revolved
of ti!~1eSin a rotating
iron cylinder.
The interior
of the cyl-
inder may be provided with iron ribs to aid the attr1tion;
times pieces of iron a.re enclosed
for the same purpose.
someThe
tests are often per rormed bo th wet and dry.
The Devalmachine
with modifications
in It'renchand American
my exper fmen t s ,
laboratories,
In principle
haa been largely used
and was the One employed
1t consists
of an iron cylinder
7.9" in diameter and 13.4" deep, the interior
smooth.
It is so mounted
with the axis of rotation
The speed of revolution
10,000 turns occupy five hours in time.
broken
so as ,to just
and the proportion
pass
being perfectly
on u shaft that the axis of rotation
of the cylinder makes an angle of 30
of the shaft.
in
through
of material
2.4"
is so regulated
that
Eleven Ibs. of rock
ring
are
used
us a sample,
less than 1/168 diameter
ascer-
tained.
Since it has been found that only the best varieties
rock yield
'tleight,
than
.2,gramdust
of 'vear.
it has been proven
Limestones
by the
As the r-esu l.t of a large
than those of sedimentary
3-10%.
to 2.2 Lbs , r ock,
the number 20 has been adopted
co-effj.cient
iments,
less
tha t igneous
origin.
or 2/~t of their
French as their
number of exper-
r-ocks are much tougher
Their total loss ranges
range from 10-35%, flints 8-26%.
of' tests vlith the Branford
of
stone the following
from
In a series
average result
was obtained:-
Per cent. Vicar, 4.20; Fr. co-efr., 11.3.
Very rew chips were ohtained, the bulk of the detritus be-
1ng the finest dust.
These results are almost identical with
those obtained by Mr. L.
ment laboratory
VI.
Page on the same rock in the Govern-
at Washington,
namely, 4.29 and 11.6.
dicate an exoellent road material,
although
their values are som~
what higher than those obtained from most diabase
discrepanoy
traps.
is due to the presence of a oonsiderable
vein material
They in-
The
quantity
of
(about 1.4% the mass of the rock); but, since, as
will be shown later, this dust has abnormally
ers, it enhances rather than deteriorates
high binding pow-
the value of the rock.
Cementation·Value.
In the case of trap rocks in particular,
this test 1s of tm
utmost value, for, in the construction
of macadam roads, the
binding power of the detrital material
plays a very important
role, and may serve to condemn an otherwise
mentation
test. as now performed,
dex of binding power.
good rock.
The ce-
yields a fairly accurate
Before describing
in-
this test in detail, a
few words on the influenoe of binding material
in the construc-
tion of a road will not be out ot place~
The conditions
ot wear to which a roadstone
result in its gradual consolidation.
ed road can never be maintained
The consolidation
by. crushing
is subjected
An impertectly
in a satisfactory
consolidat-
condition.
1s a result of the wear of the original
stones
and grinding in the road, so that on an average be-
tween 65-90'; of the broken stone put upon a road wears down ultimately to a state of mud and detritus.
the smaller the percentage
The tougher the stone,
of this detritus.
-14-
There bas been a very spirited controversy
in the past regarding
rial.
Whether
among engineers
the function and utility of binding mate-
the road should be left to consolidate
the gradual wear and tear of traffic or whether
itself by
the process
~~
should be aided and the sharp angles of the stone~by the original filling of the interstices
with binding material;
and the
to add, if any, have been much mooted
quantity of this material
questions.
The concensus of modern opinion seems to
be that the true
function of binding material 1s in fonming a thin
whicht
being ~perv1ous,
protects the broken stone heneath.
other words, a road should practically
the paramount
importanoe
face cover,
4
sID
consolidate
In
itself; heno~
of selecting material possessing
the
requisite binding power.
The oementation
material,
tests, as conduoted by me on the Branford
were as follows:
The dust obtained
test was passed through a 100 mesh sieve
then made into briquettes
and the same height,
of circular
by placing
tilled water to moisten;
The compressed
and then treated as follows:
is oomplicated.
seotion,
to a pressure
.98" in diameter,
briquettes
of 1,422 Ibs. to the
were dried two weeks,
A machine espeoially designed
laboratories
but its prinoiple
was used.
simple.
hammer,
automatically
height,
strikes a flat end plunger, of weight
Which latter. by an
It was
in a metal die with enough dis-
this test and kept in the Harvard
mechanism
(to the inch).
a closely fitting plug was next insert-
ed , and the mass subjected
square inch.
in the attrition
for
Its
A kilogram
arranged· to fall through any desired
arrangement
one kilogram,
of springs, presses on the br1-
-15-
quette.
The standard fall for the hammer is .39".
The exact
point of fracture is determined by means of a small drum oarrying a paper on which a pointer marks the passages
of the hammer.
At the beginning a rebound of the hammer Is indicated on the
drum, but when once the elastic limit of the briquette
this rebound no longer occurs.
point.
This is taken as the breaking
The number of blows required
tation is taken as representing
is passe~
to break the bond of cemen-
the binding power of the stone.
A series of tests made along
these lines yielded results
as fol1ows:No.1.
No.2.
No.3.
No.4.
40
46
43
50
The result obtained by lir. Page as given in the Company's
\vas~.
All of these
exceptionally
printed
desirable
results are abnormally
stone.
1900, in which the cementation
road metals were determined,
only eight exceeded
these values.
good road mate-
that of all road metals
in America,
only limestones
and a few traps ever exceed more than 30-40 blows without
ing.
The Highway Division
following
Trap rooks,
Serpentirtes,
and quartz rocks,
Limestones,
SandstQn~s •.
break-
of the Maryland Survey prints the
tables:
Granites
results
value for 116 samples of various
As a result of a large number of experiments
it has been detenmined
an
Conrmisnicn' s Report for
and of these only three were, in other respects,
rial.
indicating
high,
In a series of tabulated
in the lltassachnsetts Highway
Report
Cementation Tests.
1-16
10-300
1-13
1-73
.(}'28.
-16-
Cementation.
It further states that:
Bad road metal ma.y possess
Fair
"
Good
II
n
Excellent
Recementation
"
"
Ii
ff
1-4
5-10
10-20
road metal may possess
20-
Value.
It is not only important
to know the binding
but the oapacity of the particles
tritttl material,
when again wetted and dried after being powdered.
ing to Prof. Shaler~
depends
way."
To imitate,
as
the following test has
from which
The broken briquettes
value has been determined
quantities
For, accord-
the effect of the action of the "fines" under
the sharp blows of the horses' hoofs,
been devised:
to reunite
"on this process of recementa:tion largely
the endura.noe of any macadamized
far as possible,
power of de-
are repowdered,
of water, and remoulded.
the cementation
mixed with definite
The process
aCc,
1200, 16°c
of dis-
ed as above.
Using conseoutively
tilled water,
T obtained values of 46, 40, 22, 36 for the rece-
mentation
power.
40c,
1s then repeat-
Yr. Page obtained.!!
these results are unusually
as his result.
high, and indicate
All of
a splendid road
metal.
Absorptive Power.
This test does not indicate
merely
the porosity
the pounds of water absorbed
mers10n of 96 hours.
~moothly worn fragment
!t is performed
of the rock, but
per cubic foot during an 1~
with a small specimen.
left from the attrition
A
test, and weigh-
-17-
1ng
from 20-60 gra..ms, Ls ..
veighed in air.
It 1s then innnersed
in wat.er, and 1rF1medla.tely reweighed in water.
it 1s again weighed in water.
immersion
After 96 hours"
By a very
simple calcu-
lation the amount absorbed "per cubic foot is determined..
result
As tho
of a series of tests, the following values were obtained:
no.
No.1 ..
2.
These results are considerably
:Mr. Page (.83),
No.3.
No.4.
,.54
.46
lower than the value
but I feel great oonfidence
submitted
in their accuracy.
The results are still somewhat high for a normal diabase
owing? doubtless?
planes
to the extensive
calcite veining
trap,
affording
of easy penetration.
Tests.
Weathering
The liability
of stone to disinteerate
frost depends partly on its porosity
partly
by
on the presence of planes
tion planes of flagstones.
by the action
and absorptive
of
power, and
of weakneas such as the lamina.-
Tests have been devised
to imitate
the action of frost,. as, for instance,. Brar'dt s Process ...
-soaking
a weighed
allowing
sample in a saturated
to dry; and also by artificially
while saturated
ful utility
With water.
of minerals
freezing
the sample
enough to disintegrate
of doubtin this
Further,. the weathering
as a roadstone.
under atmospheric
extraordinarily
of' Glauber~s'::'saltand
These tests are, however,
since a stone porous
wa.y would be valueless
Percussive
solution
influences
is, on the whole,. an
slow process.
and Compressive
Strength.
Both these tests are restricted
in soope and of very ques-
-18-
tionable
value.
The former is somewhat used abroad, but the
result obtained b:l'the attrition
of the toughness
test gives a very fair estimato
a rock and malces the percussive
of
strength
test
superfluous.
The compressive
strength is a factor of so many variables
as to make it extremely misleading.
Inherent
pIe, small variations
structure,
in the preparation
tected.
neither
in mineralogio
of the cube introduce
tests were applied
flaws in the
S~
and carelessness
errors not ret~dily de-
to the Branford
rock.
Chemical Analysis.
A chemical analysis
alone is of little value in indicating
the ~ua11ty of a roadstone;
ment and corroborate
interest.
it is only when intended
a mineralogical
It 1s true that durability
anee to abrasion,
analysis
depends
to supple-
that it possesses
largely on resist-
and this, in turn, is influenced
by the chem-
Again, it is abso-
icn,l composition
of the ccmponent minerals.
lutely essontial
that the bottom layers of a road bed be of
chcmicz.lly durable material.
rily calculB.ted,do
points.
But chemical
as ordina-
not yield all the information on these
Such analyses do, however,
the rock.
analyses,
serve to properly
aIE:.58ify
The followine results were obtained by me on samples
of the Branford
rock:-
--=
50.01
49.28
15.62
15.92
1.91
1.91
PeO
=
10.30
10.20
1IriO
=
.40
.37
81°2
A1203
Fa203
-19-
=
lIg0
5.60
5.99
7.22
7.44
CaO
...
K20
...~
.65
.72
Na20
-=
3.80
3.40
3.10
3.90
-
H2O
-
CO2
1.14
1.20
9~
lO~
The figures in the second column represent
in the Wesleyan
analysis
laboratories
in most respects
an analysis nmde
for the Company, and checks
my
qUite accurately.
These analyses prove the rock to be a very normal diabaso
trap, as shown by a comparative
sas tabulated
study of several typical ana1y ..
in R06enbusch~
Mineralogical F~alysis.
This test is' of extreme importance
road metal.
It serves to determine
1)1e, and hence to l)roperly
structure
classify it.
It reveals
of the sumthe minute
hardness and toughness.
Several slides of the Branford
fUlly studied.
The microscope
of two minerals,
closely interlocked,
monoclinic
the composition
of a
of the rock, and thlis throws much light on the ques-
tion of durabilitYt
principally
in the selection
showed the'rock to be composed
very finely and evenly crvs ta.J.lized,
and , on the whole, fairly fresh, namely, a
and a quite basic feldspar~
pyroxene
these minerals
trap were cut axxJ and care-
were present in very subordinate
iron ore, orthoclase.
with
amounts, apatit~
quartz, chlorite, and serpentine.
The pyroxene was almost entirely augite--the
bro;vnish variety.
Associated
It eXhibited every gradation
ordinary,
from perfectly
-20.
fresh to entirely
decayed
siderablyaltered.
cleavages
oxide,
On the whole,
crystals.
Its usually
well developed
by films of iron
at right angles were often penetrated
one of the products
of whioh
of its
decompos1tion.
often imitate
the appearance
cases the decomposition
had proceeded
original
nature
of the m1neral--its
Compared
the black
of a fir tree.
stalm
In other
so far as to obscure
identity
able from its pos1t1on~ and chlor1tic
products.
it was con·
It occupied, in every caS8t the interstices
the feldspar
between
crystals.
the
being only surmis-
and serpentinio
with the other mdnerals,
alteration
the augite was the
most SUbject to decomposition.
The feldspar
laths,
sometimes
prisms.
whole,
was labradorite.
long and slender, more rarely
The crystals
remarkably
ited, more rarely
Apatite
prisms,
fresh.
Albite
Carlsbad.
was observed
negative
Zonal structure
occasionally
high sj.ngle,loYI
exhib~
not noticeable.
as thin, needle-like
and
double refraction,
with
was rarely noted.
some ilmenite
Some quartz,
the dhlorite
after augite.
terial was mostly
confined
invariably
doubtedly
quartz.
andserpent1ne
Some small, almost
to the central portion
As
were 1n every case
The latter predominated.
calcite.
and
chalodon1c
was associa.ted wi th the cal'ci:ticvein material.
before noted,
secondary
being, on the
extinction.
Orthoclase
in variety,
short and broad
twining was frequently
The iron ore was largely magnetite,
limonite.
as intergrown
were clear and colorless,
known by their
opitcnlly
It occurred
The vein ma-
isotropio
area,
of the vein, were un-
Tho rock may be ranked us a fairly fresh diabase.
De compo-
-21-
sit10n has most affected the ferromagnesiun1
constituent.
dacomposi tion products have remained tt1n, s1 tu",
vein material.
or passed into
There is no eVidence of a porphyritic
and nothing to indicate an extrusive mode of origin.
economic standpoint,
decomposition
strength of the material.
feldspar guarantees
come.
structure,
From an
has not much affected the
The firm, interlaced
the solidity
Its
network of fresh
of the rock for a long time to