Expanded markets for copper in the past few years and a consequent search for new ore bodies have revitalized the widely known but seldom applied method of producing copper called heap leaching. This term should be differentiated from dump leaching in that the latter is applied to dumps of mixed oxide and sulfide ores (although either may predominate) that have been too low grade to beneficiate and have, therefore, been stripped off the higher grade underlying sulfide ores. Heap leaching is defined here as the process applied to oxide ores which have been mined solely for the purpose of leaching.
Although heap leaching does reduce capital expenditures, it also requires extensive test work and sound engineering to produce a successful operation. A company contemplating heap leaching must insist on a definite, well planned program of investigation. Adequate exploration is a necessity to assure that high acid consuming sections are not present in the ore body and test work must be done on drill cores to determine if acid attack on the host rock will result in physical degradation which would blind a leach heap. Items such as acid consumption, seepage and evaporation losses, leaching rates and anticipated ultimate recovery must be