The Stealth Element: How Mercury Became a Global Environmental Problem

Small-scale gold mining is now the largest source of mercury released into the environment, being responsible for 37% of all global emissions. Mercury readily dissolves gold to form an amalgam, and as such is used for extracting the precious metal from gold bearing ores and sediments. When miners apply heat to the amalgam, mercury vaporizes, leaving behind pure gold. This process is employed daily by hundreds of thousands of small scale miners in developing countries, endangering their lives and polluting rivers and streams.
http://www.huffingtonpost.com/gustavo-a-b-da-fonseca/the-stealth-element-how-mercury-became-a-global-environmental-problem_b_6063108.html?utm_hp_ref=green