Heap leaching is an industrial mining process to extract metals and other compounds from ore via chemical reactions that absorb specific minerals. The ore is crushed into small chunks and heaped on an leach pad where it can be irrigated with a leach solution to dissolve the valuable metals. Hard rock mining, Sierrita Mine, Pima County, Arizona, USA © march. 27 2009 Marco van Middelkoop/Aerophoto-Schiphol