Mesozoicrocks Mining,milling, and Po eozoicrocks
STAGEl-Flqt-lying sedimenlory rocks ore deposiledo!er Precombnonrocks smeltingoperations in
Mesozolc rocks southwestNew Mexico rocxs Poleo?oic----_ -\ \ \ \ byRobert Shantz, Metallurgist, Hillsboro, NM, lormerly of NMBM&MR rocxs Precombrion \ The ultimate goal of mining and min- and open-pit. Open-pit mining is the STAGE2-Compression creoles Los Vegos syncline eral-processingoperations in southwest method of choice in areas where ore New Mexico is the production of a depositsoccur at or near the surface. relatively pure metal or nonmetallic Depositsof this type occur at SantaRita mineral. Most metals occur in chemical and Tyrone as large, low grade ore combinationwith other elementsto form bodies.Underground mining methods are minerals. These minerals are dispersed usedto recoverore in narrow, nearlyver- throughoutgenerally valueless rock-form- tical veinsand chutes(in the caseof the STAGE3-Continued compression creotes ruplureby (gangue)to form ore - rock Groundhogmine at Vanadium);or when reversefoulling ing minerals massesof sufficientsize and valueto be the ore body is coveredby too much over- processedeconomically. These ore bodies burden to remove economically(in the occur in the surroundingrock or waste caseof UV Industries).Both conditions and vary in sizefrom very high-gradeore arepresent in the area. depositsa few inchesthick in somepre- Thereare three major open-pitmines in cious-metalmines to low-gradeore depos- the district.UV Industriesat Fierro, Ken- STAGE4-Af fer compressionreloxed,normol foulling R'ita, occurredin block west of reversefoull its hundredsof feetthick in porphyrycop- necottcopper corporation at Santa per mines. The mining processremoves and PhelpsDodge at Tyrone. In the pits, FrcunE 4-GENERALTZED sEcrtoN TAKEN DUE EAsr and wasteare first brokenby drilling FROM POINT A OF CROSS-SECTIONLINE. the ore from the surroundingwaste rock; ore milling separatesthe valuable minerals holesup to 14inches in diameterand 60 ft vicinity. The most commerciallyfeasible, from the gangue; and smelting breaks deep at a predetermineddistance back simple enterprisewould be a seriesof down the mineralsto yieldthe puremetal. from the edgeof the bench.The holesare greenhouseslocated below the hot springs Various companyoperations use different loadedwith explosive,then blasted.The and heatedyear round for growing vege- equipmentand proceduresto accomplish brokenrock is loadedinto trucksby elec- tablesand flowers. thesesteps. tric shovels-someof which can moveup A more complicated,industrial genera- At present,some of the major mines, to 25 tons at a time (fie. l). Suchshovels, tion of electricity on a small scalemight mills, and smeltersin southwesternNew at present,cost in excessof a million be accomplishedthrough the use of heat Mexico are shut down as a result of dollars. Trucks used in the pits have and engines.Apparently the temperaturedif- depressed copper and zinc Prices. capacitiesfrom 40 to 150tons each, ferential betweenthe hot spring waters Although significant quantities of non- there is a trend towards even larger and the cold waterof the GallinasRiver is metallic minerals such as fluorspar were trucks. great enoughto make heat engineseco- producedin the past, presentproduction With the presentore grade at Chino nomically feasible,although a substantial is limited,except for theMathis lime plant and Tyrone, about 3 tons of wastemust capitalinvestment would be necessaryfor midwaybetween Hanover and Central. be moved for each ton of ore mined. their installation. Most of the major operatorsprovide Allowing for milling and smeltinglosses, 700lbs of rock must be Referencescited for some form of public access.During this meansabout the summerKennecott Copper Corpora- blasted, loaded, and hauled for each Baltz,E. H., 1972,Geologic map and crosssections pound produced.The Chino of the Gallinas Creek area, Sangre de Cristo tion normallyconducts tours of its opera- of copper Mountains, San Miguel County, New Mexico: tions at Hurley for the generalpublic. As mine producesabout 23,000tons of ore U.S. Geol. SurveyMisc. Geol. Inv. Map l-673 a rule, given advancenotice, both Ken- perday, Tyroneabout 46,000 tons. (sheetI of2) Phelps Dodge Corporation at Because most of the underground Bejnar,C. R., 1967,Temperature gradients of ther- necott and Tyrone are able to arrange specialgroup mines in the district have been closed mal springsat Montezuma,New Mexico, unpub- prices, lishedpaper tours. Other operators vary in their down dueto depressedmetal UV's LasVegas (NM) Daily Optic,20 April, 1885 policiesregarding public tours. In addi- ContinentalMine at Fierro is currently Lessard,R. H., and Bejnar,W., 1976,Geology of tion, PhelpsDodge, Chino, and TYrone the only one of its kind in operation. the Las Vegasarea: New Mexico GeologicalSoci havereadily accessable public lookoutsat ASARCO's (American Smelting and etyGuidebook, 27th Field Conf., p. 103-108 unit at Reinerts,T. H., 1966,A historyof the Montezuma the pits. Refining Company) Groundhog Cor- Hot Springs,hotels, and bathhouses,1849-1937:. The potential hazards of abandoned Vanadium and Federal Resources M.S. thesis,New Mexico Highlands Univ.,97 p. minesare significantand many. Do not poration'sBonney Mine at Lordsburgcan Summers,W. K., 1965,Chemical characteristics of enter abandonedmines, pits, or workings. be expectedto openiflead, zinc,and cop- New Mexico's thermal waters: New Mexico smallunderground ResourcesCirc. 83, Children in all mining areas should be per pricesrise. Several Bureauof Minesand Mineral precious- 27p. under careful supervisionat all times. minesship limited amountsof 1968,Geothermics-New Mexico's untap- metal bearingfluxing ore to the ASARCO pedresource: New Mexico Business, v. 21,no. 8 Mining smelterat El Paso,and a few other mines 19'16,Cataloe of thermal waters in New produce fluorspar on an intermittent Mexico:New MexicoBureau of Minesand Min- In general, mining operations can be eralResourcesHydrologicReport4,p.69-72 ! dividedinto two categories:underground basis.
24 May 1979 New Mexico Geology Mitling The ores produced are treated locally by various concentrators and smelters. Little direct-shipping (high-grade)ore is produced,therefore the oresare process- ed in concentratorsto separatethe metal- bearingminerals from the barren rock, or gangue.The high-gradeproduct, or con- centrate,is shippedto a smelterwhere concentratesare melted with fluxes to removefurther impurities,and finally to remove the sulfur by oxidation, leaving approximately 99 percent pure metallic copper. Sincethe bulk of the area'sproduction is copper,the productionof metalliccop- per from ore will be describedfirst; lead- zinc treatmentwill be noted later. Basi- cally, the processinvolves three steps: breakingthe copperminerals and gangue apart, separating the copper minerals from the gangue,and recoveringthe cop- per from the minerals. Becauseof dif- ferencesin concentrator design and ore composition,the three major operators, Chino MinesDivision of KennecottCop- per Corporation, UV Industries, and FrounE l-ElecrRtc sHovEL LoADrNc lsG.ToNTRUcK. Courtesy Chino Mines Division, Kennecott Copper Phelps Dodge use somewhat different Corporation. equipmentto accomplishthese steps. The first step, breaking the minerals and gangueapart, involves crushing and grinding (comminution). The ore, which comesfrom the mine as rocks up to 6 ft in diameter, is dumped into a primary crusherthat reducesthe rock to 8- to 12- inch pieces.Both UV and Chino usejaw crushersfor this step,while PhelpsDodge uses a large gyratory crusher. From the primary crusher, the ore goes to secon- dary and tertiary crushersat Chino and PhelpsDodge. Both use gyratory (cone) crushersfor the secondariesthat reduce the ore to approximately2 inches.Phelps Dodgethen usesshorthead cone crushers, and Chino, roll crushers,to reducethe ore to 3/8-inch pieces.Typically, motors of about 500-hpare usedon thesecrushers. At UV, the ore goes from the primary crushersto a semi-autogenousmill, a large diameter (30-ft) rotating drum in which the physicalaction of the ore itself tumbling with large steel balls combines to reducethe ore. At UV's No. 2 concen- trator, a 5000-hpmotor drivesthe mill. Finally, PhelpsDodge and Chino useball mills - large,drum-shaped rotating mills Frcunp 2-GnrNDrNc sEcrtoN ar Cxrxo; ball mills in foreground, cyclone classifiersat upper left. CourtesyChino Mines Division, KennecottCopper Corporation. filled with steelballs - to grind the ore to the requiredfinal size$te. 2).At Phelps mill for further grinding, smallermaterial Dodge regrinds the rougher concentrate Dodge, there are 20 of these 1250-hp goes to flotation. (At Phelps Dodge, to separatethe pyrite (iron sulfide) and primary ball mills, each12 ft in diameter about95 percent of the dischargewill pass chalcocite(copper sulfide). This two-step x 12 ft long, holding 80 tons of steel a 65-meshscreen.) UV usespebble mills approach is far more economical than balls. The dischargefrom these mills is for fine grinding. Here the final grind is grinding all the ore to the sizerequired for classified (sized) by cyclones at Phelps achievedusing lumps of ore about2- to 3- the final concentrate. Dodge and rake classifiersat Chino; the inchesin diameterrather than steelballs. The second step, separatingthe valu- larger particles are sent back to the ball After the first (rougher)flotation, Phelps able minerals from the waste,is done by r=F May 1979 NewMexico Geology 25 froth flotation. Here the water-oremix- verters(- 9g percentCu) is treated in nessbeyond; and the incomprehensible ture (pulp) comingfrom the grindingsec- reducing(anode) furnaces to removemost beautywrought over the eonsand lost to tion is agitatedin a seriesof flotation cells of the remainingimpurities (mostly ox- the world until an explorer's lamp that also introduce small air bubbles. ygen). The copper is cast in molds and discoveredits breathtakingsplendor. It Chemicalscalled collectors are addedto eithersold directlyfor brassmanufacture conveysthe surgeof pridein knowingthat the pulp to coat the small mineral par- or sent to an electrolytic refinery for fur- no human footstep has disturbed the ticles.Other chemicalscalled frothers are ther processing.Lead and zinc concen- silenceof centuries. addedto makea stablefroth that risesto trates are treated out-of-state by sig- The author has kept a concisevisual the top of the pulp. The coatedmineral nificantly different methodsto produce and written recordof his explorations,in- particleattaches itself to the foam rising metalliclead and zinc. timatelyreflecting what theseyoung men to the top whereit is skimmedoff. The saw, said, and felt during their adven- concentrate from these first cells is Summary tures.An outstandingphotographic essay refloated to produce the final concen- The major improvementsin miningand sectionreveals the awesomebeauty of the trate. Materialwhich did not float in the mineralprocessing equipment have allow- caverns.The photographs,dating from first cells (tailings)is sent to thickeners ed miningof muchlower grade ore, there- the late 1880'sthrough the 1940's,repre- wheremost of the wateris recovered,and fore extendingthe life of many minesin senta cross-sectionof the author'swork, thenon to tailingsdams. The concentrates the district. The undergroundmines, for togetherwith a few contributions(now in are thickened,filtered, and dried before example,and the first PhelpsDodge con- Nymyer's collection) by other photog- shipping to the smelter.The ASARCO centrator at Tyrone discontinuedopera- raphers. mill at Demingdiffered from the othersin tions in the early twentiesand did not The clarity, quality, and originality of that two concentrateswere produced.A reopenuntil mining was reintroducedin this publicationare outstanding.Follow- lead concentratewas first floated from 1969(as evidenced by the recentclosure of ing the caption of eachphoto is the page the pulp using chemicalsthat will not ASARCO's DemingConcentrator). Min- number where the narrative appears,ex- float zinc minerals, then an activator ing is still very cyclical,however, with the plaining the site and purpose of the pic- (copper sulfate) was added and another profitability of the operation dependent ture. The photo numbers appear in the seriesof cells produced a zinc concen- on fluctuatingmetal prices. margin near the appropriate passagesin trate. Future projections for most metal the text (a particularly helpful feature). In addition to the flotation plants, both prices, as well as recentexploration activ- Chino and Tyrone have leach plants ity, indicate that the district has con- AcxNowreocprprr-We appreciate Robert siderablefuture potential. ! Nymyer'skindness for the opportunity to reviewthis which also recover copper. A solution valuablecontribution to New Mexico's history and containing sulfuric acid is spread on the geolo gy . - Ne i la Pe ars o n leach dumps: some of the copper is dis- solvedas the solution drains through the dumps into holding ponds, from which it New books is pumpedto the precipitation plants. The Carlsbad, Caves, and a Camera, copper-bearingleach solution is passed by Robert Nymyer, published by over scrap iron in launders at Phelps ZephyrusPress, Inc., Teaneck,NJ, first Dodge and cone precipitatorsat Chino. printing 1978,318 p., 185 illustrations, The copper in solution replaces the hardcover,$14.95, softcover, $8.95. metallic iron in the scrap, producing a Corlsbad, Caves, and a Camera is a fine copperpowder (precipitateor cement deeply felt tribute to a way of life and a copper). After drying, the cementcopper part of nature that have almost disap- is sentto the smelter. pearedin this day and age.In 1927Aaron Nymyerbegan working for Ray V. Davis, Smelting pioneer photographer of Carlsbad The concentratesfrom the mills are Caverns, and has been active in cave mixed with silica and limestonefluxes and photographyand exploration ever since. meltedto producea moltenbath contain- The adventure,fascination, and beauty ing an upper wastelayer (slag)floating on of this publication will appeal to a lower copper-ironsulfide layer (matte). geologistsand non-geologistsalike. The Chino mines at Hurley usesa reverber- author recallshis cave explorationas a atory furnace for this step; PhelpsDodge young man in the 1930's-in thosedays, at Playas, a flash furnace. The molten despite an abundance of outstanding slag is hauled to waste dumps directly cavesto be discoveredand exploredin the from the reverberatoryat Chino. After Carlsbad region, caving lacked its cleaningin an electricfurnace at Phelps present-daysophistication. Dodge, the molten matte, containing This is the storyof youngamateurs who about40 percentcopper, is transferredto ventured underground-inexperienced, convertersin large ladles. Here, air is unadvised,and unguided-into an un- blown through the molten matte, oxidiz- known world. They facedtheir problems ing the sulfur to sulfur dioxide and pro- as they arose,and eventuallyacquired a ducing metalliccopper. The sulfur diox- high degreeof technicalcompetence in ide in the exhaustgas is convertedto thrill of ex- caving.The book capturesthe Tne CllNsurrN rN NEw C,c.vn,with the author sulfuric acid which is shippedto various ploringthe unknown,accompanied by the crouchingin front. This is one of the more awesome markets. Blister copper from the con- ever-presentthreat of dangerin the dark- sightsin the cave(photo takenSeptember 24,1938).
26 May 1979 New Mexico Geology