Feasibility
studyofgravitational
oreseparation,
Hansonburg
NewMexico
miningdistrict,central
byRene
S.Steensma,
Minopco
Inc.,Socorro,
NM
Abstract
In an article on the barite-fluorite-lead
minesof the Hansonburgmining district
of SocorroCounty, Kottlowski (1979)indicatedthat developmentof new milling
techniqueswould enhanceore recoveryin
the area. A pulverizerthat incorporates
the functionsof a secondarycrusherand a
jig
ball mill, alongwith a newlydeveloped
combineto makegravitationalseparation
of ore a feasibleprocess.This approachis
not only more economicalthan flotation
(the only theoreticalalternative),but also
avoids pollution and the resultant environmentalimpactproblems.
Gravitational separation
Among alternative methods studied,
gravitational separationwas the method
of choice.My previouswork on the separation of ores using magneticmaterial
with a specific gravity adequatefor the
task had provenefficient.Now, if a suitable magneticmaterial could be found or
manufactured, the following method
could be applied.After crushingthe ore
to minus3/S-inchin size,it would thenbe
preconcentrated
by a jig, thus eliminating
the principal wastefactor in the process.
After regrinding,the materialwould pass
over tables.To separatethe fluorite from
the quartz and limestone, an artificial
Introduction
magneticproduct with a specificgravity
A brief review of concentrationmeth- slightly lower than fluorite but higher
ods used in the past on the Hansonburg than quartz would be introducedto obores indicates certain problem areas. tain the requiredseparation.
First, no water was availableat the site.
The crudeore had to be transportedmore
than 40 km to a sitewhereit could be concentrated.Next, the existing techniques
failed to provide a solution to the problem-the separationof the threevaluable
minerals (galena, barite, and fluorite)
from the host rock (limestone and
q\artz).
A flotation mill obtained good lead
recoveries,and limited amountsof barite
were recoveredfrom areaswhere barite
concentrationswere high. Fluorite could
T o i l i n g so u t
not be recoveredby this process.
When Minopco took an interestin the
project, a mineral separationstudy was
undertaken.Initially, the studywasbased
on the presuppositionthat only flotation
C o n li n u o u s
could providethe desiredresults.Results,
in
however,weredisappointing,for lead reDi op h r
coverywaslow-possibly due to the presenceof lead carbonatein the ore. Barite
concentrateswere good, with high recovery values. The fluorite concentrate
E c c e n tr i c
neededto be improvedbecauseof a high
drive
leadcontent.
In addition, the flotation process
Slroke
caused the following problems: water
o dj u s im e n t
pollution, increased
waterconsumptionin
Volve plote
an area where water is scarce,complexities in plant construction, increased
energyconsumptiondue to the useof ball
mills, and the needfor morehighly skilled
Collect concenlroleJ
personnel and management-all factors
here
that increasemilling costs.
FIGURE l-TsE
The Hudsonjig
While working on this project, I met
Mr. Gene Hudson from Phoenix, Arizona, who had dedicateda substantial
part of his careerto the developmentof
cost-efficient mining equipment that
would provide economicaland practical
mining machineryto the smallerminesin
the southwestern
United States.Mr. Hudson seemsto have realizedhis goal in
developinga pulverizerand a jig, with
outstandingresults.Both machinestested
have produced excellentrecoveries,although the pulverizer has been slightly
modified to match our need for higher
capacity.
A sketchof the jig appearsin fig. l.
Movement of the jigbed can be closely
regulatedby a stroke adjustment; and
(continuedon page 58)
O r e f e e d( s l u r r y )
Volve plote
HuosoNrrc.
New Mexico Geology
November 1979
20.4 Junctionwith asphaltroad; turn right,
go northward. Note sinkholesin vary.'
ing stagesof developmentalong bluff
to east.
21.0 Lazy Lagoonon left.
22.6 Junctionwith upperroad; end of loop.
Turn left to Roswell,13.4mi.
Geology
The PecosValley near BottomlessLakesis
cut in sedimentaryrocks laid down about 230
m.y. (million years)ago in an arm of the vast
Permiansea.Periodically,whenthis areawas
a huge, shallow baylike feature,the gypsum
and reddishsiltstonesof the ArtesiaGroup of
rocks were deposited.The entire area was
tilted very gently(2'to 3") to the east.The
PecosValley was cut during relativelyrecent
geologic time in these Permian sediments.
Originally, the Pecos River flowed several
mileswestof Roswell,but the tilt of the beds
causedthe river to shift eastwardas downcutting continued.
Sedimentsdepositedin the valley by the
river are sand,somegravel,and quantitiesof
clay and silt. The presentriver channeloccupies the lowest area and is bordered by
floodplains with oxbow lakes and swamps
marking abandonedchannels(such as Lazy
Lagoonin the northwestpart of the park).
Above the floodplain,especiallyon the west
sideof the river, are higherterracescomprised
of oldersandsand silts.The upperterrace,the
OrchardPark. is about 40 ft abovethe floodplain. The lower terrace, the Lakewood, is
about 20 ft above the floodplain. Theseterrace sedimentswere depositedand truncated
during varying periodsof the Pleistocene
Ice
Age, 10,000to 20,000 years ago, as huge
volumes of glacier melt-watercame roaring
down from the Sangrede CristoMountains.
Someof theseArtesia Group rocks are exposedin road cutsalongUS-380at Comanche
Hill on the eastsideof the valleybetweenBottomlessLakes StatePark and Roswell.Here
the rocks are pink, green,and red siltstones
interbeddedwith grayishto white bedsof gypsum. Similar rock beds occur in the park,
along the roadsand surroundinglakes.
A notable feature of these beds are the
"PecosDiamonds," small,doubly-terminated
quartz crystalsfound for nearly 100mi along
the eastsideof the PecosValley,from Dunlap
in De BacaCountyto thenorth, acrossChaves
County, to just south of Artesia in Eddy
County. In areaswherethe gypsumbedscome
to the surface,as at severaloverviewsin the
park, the sparkleof sunlightfrom the quartz
crystalsis quite noticeable.Gypsum crystals
also reflect the sunlight. Perfect quartz
crystals are difficult to find, but beautiful
PecosDiamondsare prominentin the collectionsof manymineralogists.
How did the lakes form? One of the best
Gravitational
oreseparation
lcontinuedfrom page55)
various water inlets and the overflow,
which evacuatesair from the pulsewater,
allow a very subtle bed movement.The
patentedvalve systemregulatesthe suction of the movement.Thesethree variables allow concentration of material
down to 325 mesh. In the Hansonburg
district, our materialwill be concentrated
in threecarefullyscreened
groups:50-150
mesh,150-200mesh,and materialpassing
200mesh.
Resultswith the jig have been highly
satisfactory on our ore, with galenaand
barite recoverieswell above 90 percent.
Fluorspar recovery is somewhat lower
(70-80 percent). The remaining tailings
will be treated by gravity separation,
using magnetic material as previously
mentioned.The price of fluorspar at the
moment does not warrant recoveryfrom
the tailings.It will be stockpileduntil better pricesjustify further processing.
The pulverizer (fig. 2) is basicatlysimilar to any other pulverizer. The most
significantdifferenceslie in the designof
the breakingplates,the rotor outlet, and
the rotor itself. The useof specialwedgeshapedsteelplatesand the curvatureof
November1979
New Mexico Geology
P u l v e r i z e do r e
collecled here
placesto comprehendtheir origin is at the
overlook above Lea Lake where the bluffs
coincidewith a sharp flexure in the Artesia
Group beds.The regionaldip is gentleand to
the east, yet along this river-valley escarpment, the dip is rather steepto the southwest.
The pronouncedreversalof dip is probably
due to the solutionof gypsumand consequent
slumping of overlying beds. Underground
channelsand cavernswere dissolvedout by
circulating ground water, resultingin deep,
depressionsnow filled by the
steep-walled
lakes. These collapse structurescausedby
ground-water solution of rocks are called
sinkholes.
The lake water, fed from salty underground
flow, is high in sulfates(4,000to 14,000ppm)
from the gypsumbeds.Thus the necessityof
piping in water from Roswell-to make the
swimmingmoreenjoyable.
Flora and fauna
Among the vegetationin the valleyare mesquite, creosotebush, salt brush, salt grass,
snakeweed,salt cedar(tamarisk),yucca,and
cactus.Sparsegrassand scatteredshrubsconservethe sandysoil of the uplands.
Roadrunners and jackrabbits rule the
brush. Rare fish, such as the zebra killifish
and Texas cyprinodon, inhabit the salty lake
waters.
!
-F. E. Kottlowski
NMBM&MR
This systemhas the following advantages.1) Powerconsumptionfor processing copperore was 35 percentlessthan a
secondarycrusherand a ball mill would
haverequired. 2) Capital cost savingsas a
result of the elimination of secondary
crushingand milling when these operations are combinedinto a singleprocess.
3) Reducedmaintenancecostsdue to reduced wear and lessdown time. 4) Machineoperateson a limited water supply,
and at low pollution levels. 5) Minimal
skillsarerequiredfor operation.
Because these advantagesmay encourage successfulmining ventures in
more remote areas, the developmentof
this type of machineryis both economicallysoundand essential.
Acknowledgments
My thanks to Dr. Frank Kottlowski,
Director; Robert W. Eveleth, Mining
the ore-breakingplatesmaintain the im- Engineer;and Neila MacDonald, Assopact force perpendicularto the plates,
ciateEditor, NM Bureauof Mines& Minthus holding plateswear to a minimum. eral Resources,without whose help this
The lid can be lifted hydraulically and paperwould not havebeenpossible.
easily swung aside. The ring containing
Referencecited
the breaking plates can be removed in 5
mines
minutes;the rotor is similar in design- Kottlowski, F. 8., 1979,Barite-fluorite-lead
plates are attached of the Hansonburgmining district in central New
the tungsten-carbide
Mexico, lz New
Geology:NM Bureau of
with a few bolts, enablingtheir replace- Mines& MineralMexico
v. l, no. 2,p. 17-20_
Resources,
mentin a matterof minutes.
FIGURE 2-Tnn puLvEnrzpn.