Heap Leaching

Heap leaching is an industrial mining process to extract precious metals, copper, uranium, and other compounds from ore via a series of chemical reactions that absorbs specific minerals and then re-separate them after their division from other earth materials. Comparable to in situ mining, heap leach mining differs in that it uses a liner to place amounts of ore on, then adds the chemicals via drip systems to the ore, whereas in situ mining lacks these pads and pulls pregnant solution up to obtain the minerals. This method is only slightly more friendly environmentally, however, and has still seen copious amounts of negative feedback from both environmentalists and health experts in the past twenty or more years. Since its original peak of popularity in the 1970s, the heap leach mining technique has been applied throughout the earth, but due to recent increases in negative environmental impact assessments has received more discussion regarding rehabilitation than perpetuation of these types of mines. Yet this method continues to be a profit-earning endeavor for many mining companies across the globe.

The process has ancient origins; one of the classical methods for the manufacture of copperas (iron sulfate) was to heap up iron pyrite and collect the leachate from the heap, which was then boiled with iron to produce iron sulfate