The presence of copper in ores containing noble metals results in a high consumption of cyanide during leaching, which is undesirable from economic and environmental standpoints. Substantial previous work targets copper-gold ores, but the present study focuses on a copper-silver ore, which will be leached following acidic pretreatment (sulfuric acid at pH 1) to assess the effect of copper in cyanide consumption and silver extraction. The ore is mainly composed of hematite/goethite and silicates, with copper (0.15%) and silver (250 ppm) mostly present as sulfides and sulfosalts. The acidic pretreatment dissolves 18% of the copper content, which in turn decreases the cyanide consumption from 7 to 3 kg NaCN/ton in a five-hour leaching. Mineralogical changes, followed by polarization microscopy, are only minimal and restricted to iron oxides, while silicates and sulfides remain unchanged. Ho...