All that glitters can have a foul back side: Mercury and gold mining in the Democratic Republic of the Congo

Using mercury to extract gold from the surrounding soil dates back hundreds of years. It is an easy and cheap method that leaves the remaining gold clean.⁽¹⁰⁾ The process works as follows: soil that contains small amounts of gold is mixed with mercury, making an amalgamation of gold and mercury.⁽¹¹⁾ The gold and mercury alloy is then heated in so-called ‘gold shops’ and the mercury, which has a lower boiling point than gold, evaporates, leaving only the gold.^{(12)
http://www.polity.org.za/article/all-that-glitters-can-have-a-foul-back-side-mercury-and-gold-mining-in-the-democratic-republic-of-the-congo-2012-12-12}