Heap leaching is an industrial mining process that extracts precious metals from ore through a series of acidic chemical reactions. During this process the non-valuable earth materials or gangue are put through a series of acidic chemical reactions that absorb specific minerals and reseparate them. Comparable to in situ mining, heap leach mining differs in that uses a heap pad to separate the ore. The process begins by physically wetting and agitating the milled ore to form small spheres, rather than fine particles that can hinder the acid percolation at the heap pad site. It is then placed on a heap pad while diluted acid is added via a drip system. After the leaching process is completed, the pregnant leached solution is further processed by solvent extraction to further purify the copper solution.