Blood diamonds/Gold: 10 reasons to care where your jewelry came from

Many minors rely on mercury to separate gold from unwanted minerals. As a result, gold mining is responsible for 30 to 40 percent of man made mercury pollution each year, making it the second leading cause of mercury pollution after coal fired power plants.

Industrial gold mining uses cyanide during the gold extraction process. Like mercury, this toxic chemical inevitably leaks out and contaminates the surrounding environment.
http://www.sanskritimagazine.com/ethical_living/blood-diamonds-10-reasons-care-jewelry-came/