Gold is a very common mineral that is mined and processed in the United States and all over the world. One of the most common processes used for the mining and processing of gold in the United States is heap leaching. “The extraction of gold from low grade deposits has been one of the main factors in higher output since the 1970s” using this form of mining (www.pamp.com).
Half of all production, in the United States, of low-grade minerals comes from heap leaching. It is a low cost, effective process, which began at the Placer Development's Cortez open pit in Nevada in 1973 (www.pamp.com). Heap leaching “recovers gold from sub-grade mine waste or mill tailings.” The “native gold is taken into solution as gold cyanide and recovered by adsorption and activated carbon” (Halleck 2/19). It is very effective in removing gold from deposits filled with many other minerals as well.
The ore removed from the heap leaching is discarded onto open-air leach pads. Cyanide is then sprayed over the ore and sits there for several weeks allowing the cyanide to seep into the deposit. The cyanide extracts the gold from the ore and drips off of the leach pad on which the ore deposit sits. The gold solution runs into the “pregnant pond” where it is then pumped to the recovery plant. Zinc dust is then added to the solution causing gold and silver to precipitate. This product is then sent to refineries where the gold and silver are separated from each other (www.blm.gov).
The use of cyanide is a great environmental hazard. The cyanide affects the area in which it is used as well as the community surrounding the area of the mine. Some examples of cyanide causing hazardous situations are at the Zortman-Landusky Mine in Montana, the Summitville Mine in Colorado, the Kantor Gold Mine in Kyrgyzstan, Asia, and the Aural Gold Plant in Romania. At the Zortman-Landusky mine 52,000 gallons of cyanide solution drained into the fresh water supply of a nearby town. The Alamosa River...