Most gold mining is accomplished by extracting very fine particles of gold distributed within matrices of ore. This requires grinding the ore in order to expose the gold particles. The gold particles are then dissolved through a chemical treatment called 'leaching'. Finally, the gold is removed from the pregnant solution via one of a number of secondary recovery methods.
Almost universally, cyanide solutions are used to leach gold from ore. But not only is cyanide a very significant poison in its own right, over time, its actions also liberate heavy elements (such as cadmium, lead, mercury, etc)
“Cyanide is the most popular chemical used by mining corporations to extract gold from ore, despite the fact that leaks or spills of this chemical are extremely toxic to fish, plant life and human beings." Source which can leak into water supplies even long after initial cyanide toxicities have dissipated.”
Given the growing list of environmental mishaps caused by conventional leaching, it comes as no surprise that government policies around the world are making it more and more difficult for mining corporations to carry out cyanide operations.(Read some related press.)
In response to the environmental hazards associated with conventional mining practices, Norman Haber developed the Haber Gold Process (HGP) -- an environmentally friendly gold mining technology that also offers additional advantages over cyanide methods.