The electron microprobe at the U.S. Bureau of Mines was used to study the chemistry of the ore and gangue minerals in a suite of oxide copper ores before and after laboratory core leaching experiments using sulfuric acid. The geologic variables of ore mineral purity, gangue reactivity, and copper distribution determined the leaching characteristics of these specimens. Atacamite (60 wt pct cu), chrysocolla (25 wt pct cu), and copper- bearing clay (6 wt pct cu), the principal ore minerals present in the suite, leached in that order. Biotite, chlorite, and smectite were the most reactive gangue minerals. This mineral assemblage scavenged copper from solution. Sericite and limonite were slightly reactive in the sulfuric acid. Quartz, k-feldspar, and plagioclase did not react with acid in any strength. Fracture-hosted mineralization produced a high-grade pulse of pregnant leach solution at the start of the experiments. Disseminated ores gradually built up to steady copper loadings in solution.
Engineering Foundation Conf., Santa Barbara, California, Oct. 25-30, 1987; Eng. Foundation, Pp 81-98