Note: This article was adapted from this link and revised.
Cyanide—a rapidly acting, potentially deadly chemical—combines easily with many metals and is traditionally used in the gold mining industry to separate gold from their ores.
‘Cyanide’ can mean any one of various compounds containing the chemical group CN: one atom of carbon (C) and one atom of nitrogen (N). Usually, gold miners use a sodium cyanide solution to leach gold from ore.
There are two types of leaching:
- Heap leaching: Piles of crushed ore are spread atop giant collection pads and sprayed with cyanide solution in the open. As the cyanide trickles through the pile, it dissolves the gold from the ore into the solution. The pads collect the now metal-impregnated solution that is stripped of gold and resprayed on the heap until the ore has depleted.
- Vat (or tank) leaching: The ore is mixed with cyanide solution in large tanks, meaning there are lower chances of spills because the leaching process is more controlled. But a drawback is that the resulting waste, or tailings, is stored behind large dams (tailings storage facilities) that can and do fail catastrophically.
The efficient nature of cyanide leaching allows for the profitable mining of much lower ore grades. However, to obtain the same amount of gold from lower-grade ores, much more ore needs to be extracted and processed.
This is partly why modern mines are much larger than before cyanide was used, result in vast open pits, and create huge quantities of waste. Producing enough gold for a typical gold ring generates more than 20 tons of mine waste.
Furthermore, cyanide is highly toxic—it can cause severe environmental impacts and public health risks if discharged into the environment. Cyanide spills have led to major fish kills, polluted drinking water supplies and damaged agricultural lands.
At a gold mine in Kyrgyzstan in 1998, a truck carrying two tons of sodium cyanide crashed into a river, resulting in over 2,000 people seeking medical care.
In 2000, a tailings dam rupture at a gold mine in Romania caused 3.5 million cubic feet of cyanide-contaminated waste to spill into the surrounding rivers. This killed fish and poisoned water supplies as far as 250 miles downriver in Hungary and Yugoslavia.
The gold mining industry asserts that cyanide is relatively safe as it breaks down rapidly in surface water. But the compounds that cyanide breaks down into can be noxious.
Cyanide spills into groundwater can remain for long durations and poison drinking water aquifers. Groundwater polluted by cyanide can also contaminate hydrologically adjoining streams.
Today's hardrock mining industry too often spills cyanide, and billions of gallons of toxic chemicals have been released into the environment since the 1970s. Spills and leaks— which continue to this day—threaten the environment, wildlife and humans.
The gold mining industry can adopt a readily available solution that curtails the repercussions of mining.
Clean Mining, a part of Clean Earth Technologies, delivers a clean gold recovery process that removes cyanide as the primary means of leaching gold in medium to large-scale mining operations. Instead, we employ a non-toxic, non-flammable reagent to dissolve gold from ores before recovering the gold with resin.
We offer the safest and most sustainable gold processing reagent developed to date, with benefits for governments, mining companies, communities and consumers.