A ferrous chloride-oxygen leaching system was investigated by the federal Bureau of Mines to determine its effectiveness for recovering copper and silver from a tetrahedrite concentrate that had been pretreated to remove a majority of the antimony. The pretreated concentrate contained copper, silver, lead, zinc, antimony, and arsenic. Parameters affecting metal extraction (such as temperature, pressure, amount of ferrous chloride, and initial hydrogen ion concentration) were studied. Copper extraction of 98 pct was achieved by leaching 4 hours at 40 pounds per square inch gage (psig) and 100 deg c. Copper was recovered from leach solutions by cementation with iron, and the resulting ferrous chloride was recycled. Leaching the residue with cyanide followed by electrowinning recovered 99.7 pct of the silver. Iron, antimony, arsenic, and sulfur reported to the tailings.