What is cyanide?
Cyanide is a chemical made up of Carbon and Nitrogen, CN. Hydrogen cyanide is a colorless gas with a faint, bitter, almond-like odor. Sodium cyanide and potassium cyanide are both white solids with a bitter, almond-like odor in damp air.
In certain plant foods, including almonds, millet sprouts, lima beans, soy, spinach, bamboo shoots, and cassava roots (which are a major source of food in tropical countries), cyanides occur naturally as part of sugars or other naturally-occurring compounds.
What is cyanide used for?
About 1.4 million tonnes of hydrogen cyanide (HCN) are produced annually worldwide, of which only about 18% is converted into sodium cyanide (NaCN) and 14% of this mainly used in the extraction of precious metals such as gold and silver, and others (e.g. copper). The remaining 82 % of the hydrogen cyanide (HCN) is used in electroplating, metallurgy, and in the production of a wide range of chemicals, such as plastics, fire retardant, cosmetics, dyes, nylon (33%), paints, pharmaceuticals, Plexiglas, rocket propellant, and road and table salts.
Newmont uses approximately 1.5% of the total world production of hydrogen cyanide or 10% of cyanide production used in the mining industry.
How is it used in the gold mining industry?
Sodium cyanide is the most effective chemical known for the extraction of gold and silver from rock. It is added to water to create a solution of sodium cyanide. This is placed on crushed heaps of rock containing gold or into large tanks containing the ground up, gold bearing rock. The gold and cyanide form a strong bond and when most of the gold has been removed from the rock the gold is removed from the solution. Both the heaps and the tanks include at least double containment to insure no releases of the solution to the environment.
After gold and silver extraction, the liquid that still includes cyanide solution is recycled and reused for gold and silver extraction.
What are the risks with cyanide and the gold mining industry?
The main risks associated with cyanide are exposure of workers to concentrated hydrogen cyanide gas, leaking of cyanide into the environment and exposure of surrounding communities to cyanide due to accidental releases.
How can workers be exposed to cyanide?
Workers at gold mining operations can be exposed to cyanide during the heap leaching or tank extraction process. Controls are in place to ensure workers are not exposed to concentrated levels of hydrogen cyanide.
Cyanide can and is used safely in the extraction of gold and silver. Newmont has used cyanide in precious metals recovery processes for approximately 40 years. Over that period no one has ever died from cyanide at Newmont operations.
As a matter of interest smoking cigarettes and breathing smoke-filled air during fires are major sources of cyanide exposure.
Why is cyanide dangerous?
In large amounts cyanide is very harmful to people, it is a fast acting poison in the human body. It affects our ability to breathe. Severe breathing difficulties develop very rapidly when cyanide is swallowed, inhaled or absorbed through the skin. If people are exposed to concentrated levels of cyanide it can be lethal.
There have been no reports that cyanide can cause cancer in people or animals.
Cyanide has not been reported to directly cause birth defects but in tropical regions where mothers have been known to eat cassava root some children have been born with thyroid disease.
What happens to cyanide if it gets into the environment?
Cyanide quickly breaks down in sunlight and when exposed to air and in surface water cyanide will form hydrogen cyanide, evaporate and decompose to ammonia and carbon monoxide. It is also not known to build up the tissue of fish. Governments stipulate strict surface and ground water limits for cyanide. Any spills to the environment are typically small and are cleaned up and returned to processing facilities quickly.
How can communities be exposed to cyanide?
The cyanide used at the mine site is transported from the manufacturing plant to the mine site. If there was a road accident involving the container that carries the cyanide communities may be exposed.
If people gain unauthorized access to the mine site and are aware of the hazards and their location they may be exposed to cyanide.
How do gold mining companies manage cyanide?
The International Cyanide Management Code was developed by multi-stakeholder group for the Manufacture, Transport and Use of cyanide in gold mining. This Code provides direction and guidance on how to manage cyanide to ensure protection of workers, the environment and the communities adjacent to mining operations. Mine sites will be audited every three years by third party auditors.
How does the International Cyanide Management Code protect workers, communities and the environment?
The Code can be found at www.cyanidecode.org. A partial list of the protection mechanisms in the Code include:
