Earthworks

Cyanide Use in Gold Mining

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What is cyanide?

Cyanide is a rapidly acting, potentially deadly chemical.

“Cyanide” can mean any one of various compounds containing the chemical group CN: one atom of carbon (C) and one atom of nitrogen (N). Because it is organic, it reacts readily with living organisms.

Cyanide easily combines with many metals – making it useful in separating metals like gold from their ore.

How is cyanide used in mining?

A sodium cyanide solution is commonly used to leach gold from ore. There are two types of leaching:

Cyanide's efficiency makes mining more wasteful

Because cyanide leaching is very efficient, it allows profitable mining of much lower ore grades.

Mining lower grade ore requires the extraction and processing of much more ore to get the same amount of gold. Partially due to cyanide, modern mines are

More than 20 tons of mine waste are generated to produce enough gold for a typical ring.

What are the dangers of using cyanide?

Cyanide is highly toxic, and can result in substantial environmental impacts and public health risks if released into the environment. Cyanide spills have resulted in major fish kills, contaminated drinking water supplies and harmed agricultural lands. For example:

Cyanide spills can persist in the environment

Industry claims cyanide is relatively safe because -- even if it spills -- it breaks down rapidly in surface water. 

But the compounds that cyanide breaks down into can be harmful.

Cyanide spills into groundwater can persist for long periods of time and contaminate drinking water aquifers.  Cyanide contaminated groundwater can also pollute hydrologically connected neighboring streams.

For example, at the Beal Mountain Mine in Montana which closed in 1998, cyanide seeped into groundwater that feeds neighboring trout streams, resulting in cyanide violations in those streams long-after the mine closed.

Source: Tetra Tech, 2006 Surface Water Quality Monitoring Summary, Beal Mountain mine.

The bottom line

Today's hardrock mining industry too often spills cyanide, billions of gallons of contamination released into the environment since the 1970s. Spills and leaks – which continue to this day – endanger the environment, wildlife and humans.


For more information:

Tagged with: mining, heap leach, cyanide

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