Use of Mercury for Artisanal and Small-Scale Gold Mining


This specific issue became evident to me when I surfing twitter. Artisanal and small-scale gold mining (ASGM) is the extraction of minerals by miners working in small and medium sized operations, using rudimentary techniques.  Simple practices with minimum economic investment are employed be these miners. It is the largest intentional-release source of mercury in the world.

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How can mercury be used for gold-mining? Mercury is used to separate and collect the gold from the rocks. Mercury binds with gold to form an amalgam which facilitates it to separate from rock, sand or other material. The amalgam is then heated to vaporize the mercury leaving the gold behind.

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Mercury is a powerful neurotoxin that is harmful to people, especially to developing fetuses, and young children. Once emitted, it can travel great distances through the atmosphere, causing global contamination of ecosystems, fish, birds, mammals, and the human food chain.Local exposures in mining communities that use mercury can be acute.

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What to do now?

  1. The most important measure a mining community can take to reduce its mercury use is to concentrate the gold-containing portion of the ore before adding mercury. This can be done by crushing and grinding the ore and then using carpeted or magnetic sluice boxes or gravity concentration techniques such as panning or centrifuges. In this way, more gold will be captured, less mercury will be required and residual mercury can be more completely captured.
  2. Protective measures include the use of retorts when burning amalgam and the use of gloves by those handling mercury or amalgam.
  3. Most promising technology to replace the use of mercury is cyanidation, but this method may not be affordable or technically available to all artisanal miners. Also, cyanidation methods must be used with care and carefully introduced due to its significant risks to human health and the environment.

For further info check reference texts http://www.unep.org/hazardoussubstances/Portals/9/Mercury/AwarenessPack/English/UNEP_Mod3_UK_Web.pdf

http://www.unep.org/hazardoussubstances/Portals/9/Mercury/Documents/ASGM/Techdoc/UNEP%20Tech%20Doc%20APRIL%202012_120608b_web.pdf

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