- Kacos2000, via Flickr
- Some 90 percent of gold mines around the world employ "cyanidation," the use of a sodium cyanide compound to separate the gold from finely ground rock. At a gold mine in Romania in 2000, the accidental release of 100,000 cubic meters of cyanide-rich waste into the local watershed killed all aquatic life in nearby waters and cut off water supplies for 2.5 million people.
E — The Environmental Magazine
Dear EarthTalk: Most gold mining operations use cyanide to extract gold from surrounding rock. What are the environmental implications of this, and are there alternatives? — J. Pelton, via e-mail
Although “cyanidation”—the use of a sodium cyanide compound to separate a precious metal from finely ground rock—has become less common in other forms of mining, it is still the dominant practice in gold mining. Some 90 percent of gold mines around the world employ cyanidation to harvest their loot.
“In gold mining, a diluted cyanide solution is sprayed on crushed ore that is placed in piles or mixed with ore in enclosed vats,” reports the State Environmental Resource Center (SERC), a project of the non-profit Defenders of Wildlife. “The cyanide attaches to minute particles of gold to form a water-soluble, gold-cyanide compound from which the gold can be recovered.”
But of course not all the cyanide gets recovered. Some of it gets spilled, and some is left within mine waste that is often buried underground woefully close to groundwater, leaving neighbors and public health officials worried about its effects on drinking water and on surrounding ecosystems and local wildlife.
This article appears in Nov 3-9, 2011.