Mercury Usage in Gold Mining and Why It Is a Problem

ILLEGAL GOLD MINE, PHILIPPINES. Diwalwal. Ore is put in to rotating drums which powders the rock. Mercury is added which combines with the gold.
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Small-scale gold mining operations sometimes use mercury to separate the gold from other materials. First, mercury is mixed with the materials containing gold. A mercury-gold amalgam then is formed because gold will dissolve in the mercury while other impurities will not. The mixture of gold and mercury is then heated to a temperature that will vaporize the mercury, leaving behind the gold. This process does not result in gold that is 100 percent pure, but it does eliminate the bulk of the impurities.

The problem with this method is the release of the mercury vapor into the environment. Even if equipment is used to catch the vapor, some still can get into the atmosphere. Mercury also can get into the soil and water if it still is contaminating other waste materials from the mining process that may be discarded.

History

Mercury first was used to extract gold as many as 3,000 years ago. The process was prominent in the U.S. up until the 1960s, and the environmental impact on northern California is still felt today, according to sciencing.com.

Health Effects

Mercury vapor negatively impacts the nervous, digestive, and immune systems, and the lungs and kidneys, and it can be fatal, according to the World Health Organization. These health effects can be felt from inhaling, ingesting, or even just physical contact with mercury. Common symptoms include tremors, trouble sleeping, memory loss, headaches, and loss of motor skills.

A common means of becoming infected is through eating contaminated fish.

Still in Use

The Guyana Shield region (Surinam, Guiana and French Guiana), Indonesia, The Philippines and part of Western Africa’s coast (e.g., Ghana) are particularly impacted by the phenomenon. Under the socio-economic and political conditions found in the small-scale gold mining operation, the use of mercury is often considered as the easiest and most cost-effective solution for gold separation.

Alternatives

Gold is heavier than most other particles, so alternative methods typically use motion or water to separate the gold from lighter particles. Panning involves moving sediment that potentially contains gold in a curved pan with water and moving in such a way that any gold will settle at the bottom while the water and other particles will leave the pan. Sluicing involves sending sediment down a platform with water. The platform has a carpet-like material at the bottom that will catch the heavier gold particles while the water and other particles wash away.

Other more complex methods involve magnets, chemical leaching, and smelting.