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Technology, Care Keys to Gold Recovery Process Designed for San Luis Project Gold in Costilla County isn't in nuggets or rich veins. It occurs as microscopic specks in the tacks of the ore body. At the San Luis Project, there is only about 0.04 of an ounce of gold in each ton of ore. Extracting gold con- ~nt which is invisible to the naked eye requires a highly engineered process and pain- staking care. The mine at the San Luis Project will produce a total of about 12.2 million tons of ore over an expected mine life of about eight years. To get al the ore, some 23 million tons of overburden also will be mined. Mining will take place first at the 20- acre East Pit and then at the 110-acre Wesl Pit. Using front-end loaders and haul trucks, ore will be stockpiled and gradually fed into the mill at the rate of about 4,8170 tons of ore per day. Battle gold clings to coarse particles of activated carbon. The carbon panicles are specially manufactured from coconut shells. The carbon is then screened from the fine waste material, and in a frost set of tanks, another reagent solution strips the gold from the carbon. The result is a gold- laden, or "pregnant," Gold Ore ~~ Crushing & ling Carbon-in-Leach Tanks _ _ "Electrowinning" - Process Dore Bullio~ F Furnace Mountain Gold has set a production target of 60,000 ounces of gold per year beginning in 1991, based on the expectation that 92 percent of [he gold in each ton of ore will be recovered. MILLING At the mill, crashers will break the ore down and ball mills will grind it to the consistency of fine sand. The sandy material is "slurried" in large tanks by mixing it with water, lime, and awatered- down form of the reagent sodium cyanide. Isolated from the surrounding environment in the series of closed tanks, the reagent goes to work immedia[ely. dissolving the gold from the ore. Gold-bearing slurry flows through another series of tanF:s where the dissolved solution ready for final exvac[ion. GOLD RECOVERS' The removal of neazly pure gold from solution is accomplished by a process called "elecvo- winning;' akind of electrolysis. An eleclncal current passing through the solution actually plates the gold onto something resembling steel wool. One more step isolates the gold, as the gold-pla[ed steel wool is melted in a furcate and poured into molds to form bars. When the molten metal hardens, the small amounts of impurities which cling to the bar are hammered away, leaving a bar of dore (pronounced "DOOR-RAY"). Bars of dore, which is mostly gold with a little silver mined in, are shipped elsewhere for funher refinement. Ivtost of the ma[erials involved in the process are used again and again. "Barren" carbon, from which gold has been stripped, is resumed to the tanks containing leaching solutions. The fine waste material from which the gold-bearing carlwn has been removed is vested and pumped to a site for permanent disposal, process solutions and water separated from the slurry are recycled to the mill. the ' `f :~R . - ".~'eoti,aily will ::..'iti;r~t*.'itc~lf",I7rrii~lU~rlir maiiinv" a ;¢oildutg the ~$I7r(ItIe,SfQCkprk arp, do v ' ~ ~ t =;sit~~'f~ie#'ptp, ;~spalube iiiecharuc:artd ~YFiQh'ti+e been ' ' -';Vd'e nhiiing attdthey ~- havenl~l%eii s~ saidf3Qdsat.The protect is_ W limhg most of its peimaiier'C otlc #'a'icE`f'iom Costilla Courdy: "Otir le are very depend- able; Zlrey ; ` , ~aloi of jSiide in whaz they do. ThaP very imporAarrt to trs." New hi ate all put through an uriertsive saf arauting progmttr trader the dopcfion c~ Ron Zamwalt, safety supervisor; forftte San Ltris Project The training pmg~n'centers on regtrlations tbrrcemhtg ntNal mining enforced by the Mine Safety and Health Administra- fion (MSHA) of the itS. Depvmtent of Cabot. BaWe Mountain's safety program also irrcfudes ~ random drug scieerilng progrurrt. "AI1 of our people are passing." Dodson said "We have a drug free work force. I'm real proud of them." San Luis Project Battle Mountain Gold Company P.0. Box 3l0 San Luis, Colorado 81 152 POSTAL CUSTOMER