Abstract: A process for hydrometallurgically recovering copper from concentrates of chalcopyrite and other sulfide and mixed sulfide ores utilizes the pretreatment step of fine grinding of the concentrates coupled with subsequent leaching steps. As a pretreatment for the copper-containing concentrates, the concentrates are ground, preferrably with an attritor-type grinding device, to reduce the particle size of the copper bearing concentrate to one micron or less in size. The finely ground copper concentrate is then leached in an acidified ferric sulfate solution to recover the copper contained therein. Following the leching step, a solid-liquid separation is effected. Elemental sulfur may be recovered, and iron removal is achieved by crystallization of iron salts. Ferrous ion is then oxidized to ferric ion for recycling to the leaching step.