Gold mining has been a dirty process for more than 4500 years, with conditions worsening as easily accessible deposits of gold have declined and open pit mining has become more widespread. Open-pit mining, cyanide heap leaching, and amalgamation are dirty gold practices found throughout the world.
Two-thirds of newly mined gold comes from open-pit mining rather than the more expensive alternative of underground shaft mines. In open-pit mining, companies must remove vast amounts of rock and materials and blast the entire site. This leads to the destruction of the environment at the mine site, damage to the surrounding ecosystem, and the opening up of vast craters. Open-pit mines produce eight to ten times as much waste rubble as underground mines.
After being brought to the surface, the ore must be processed to extract the mineral, which also generates huge quantities of waste. The amount of recoverable metal in even high grade ores is generally just a small fraction of their total mass. Every ounce of gold produced results in 30 tons of mine waste.
Further Reading
Dirty Metals (No Dirty Gold, 2004)
Gold is commonly extracted from the ore through a technique called "heap leaching." The ore containing the gold is crushed, piled into heaps, and sprayed with cyanide, which trickles down through the ore and bonds with the gold. The resulting gold-cyanide solution is collected at the base of the heap and pumped to a mill, where the gold and cyanide are chemically separated. The cyanide is then stored in artificial ponds for reuse. Each bout of leaching takes a few months, after which the heaps receive a layer of fresh ore. Given the scale and duration of these operations, contamination of the surrounding environment with cyanide is almost inevitable.
To dispose of the leftover ore contaminated with cyanide and other toxins, also called tailings, a mine gradually constructs a dam. These dams are often structurally unsound. In the last 25 years, dam failures have accounted for three-quarters of all major mining accidents. In 2000, a gold mine resulting from a tailings dam failure in Romania spilled more than 100,000 gallons of cyanide-laced mine waste into the Tisza River, killing 1,240 tons of fish and contaminating the drinking water of 2.5 million people.
Further Reading
Dirty Metals (No Dirty Gold, 2004)
Amalgamation is a commonly used gold extraction process that unleashes widespread mercury contamination and continues to poison local ecosystems. In amalgamation, mercury is first brought into contact with gold, resulting in a solution of gold in mercury or an alloy of gold and mercury called amalgam. After the mercury has gathered in the gold it can be removed by dissolving it in nitric acid or by evaporating it with heat. The gold remains behind.
Small scale gold mining often relies on this process to extract gold, releasing vast quantities of mercury vapor into the environment. Mercury vapor has serious health consequences for both animals and humans. The amount of vapor released by mining activities has been proven to damage the kidneys, liver, brain, heart, lungs, colon and immune system. Chronic exposure to mercury may result in fatigue, weight loss, tremors, and behavioral and personality shifts.
Gold Mining as a Source of Mercury Exposure in the Brazilian Amazon (Malm, Olaf. Environmental Research, Volume 77, Issue 2, Pages 67-178, May 1998)
Open-pit mining, cyanide heap leaching, and amalgamation are dirty gold practices found throughout the world.
