A guide to leading practice sustainable development in mining

Cyanide
Introduction
Cyanide is a useful industrial chemical and its key role in the mining industry is to
extract gold. Worldwide, mining uses about 13 percent of the total production of
manufactured hydrogen cyanide while the remaining 87 percent is used in many
other industrial processes, apart from mining (Environment Australia 1998). In
Australia the mining industry uses about 80 percent of cyanide produced by the
country’s two cyanide producers. Cyanide is manufactured and distributed to the
gold mining industry in a variety of forms. Sodium cyanide is supplied as either
briquettes or liquid, while calcium cyanide is supplied in flake form and also in liquid
form. Calcium cyanide, if used, may contain some carbide from its manufacture and
present a risk of explosion from acetylene generation.
The hazard of cyanide derives from its property as a fast acting poison. Cyanide
binds to key iron-containing enzymes required for cells to use oxygen and as a result
tissues are unable to take up oxygen from the blood (Ballantyne 1987; Richardson
1992). In the absence of first aid, intake of toxic amounts of cyanide from gas
inhalation, or ingestion or absorption through the skin, can kill within minutes. Low
levels of cyanide from the consumption of foods are removed from the body by the
liver. Cyanide is not carcinogenic and people who suffer non-fatal poisoning usually
recover fully. However, chronic sub-lethal exposure above the toxic threshold, or
repeated low doses, may cause significant irreversible adverse effects on the central
nervous system and onset of Parkinson’s syndrome.
Since its first use in mining in New Zealand in 1887, sodium cyanide has played a key
role in extracting gold and other metals such as silver, copper and zinc from ores
worldwide. Indeed about 80 percent of the world’s gold production utilises cyanide in
extraction, with about 2500 tonnes of gold being produced annually worldwide.
Despite its high human toxicity, there have been no documented accidental human
deaths due to cyanide poisoning in the Australian and North American mining
industries over the past 100 years which indicates that the hazard of cyanide to
humans has been controlled by minimising the risk of its handling and of industrial
exposure. One significant breakthrough has been the adoption of the International
Cyanide Management Code.
A GUIDE TO LEADING PRACTICE SUSTAINABLE DEVELOPMENT IN MINING 99