The main copper sulphide minerals are chalcopyrite (CuFeS2) chalcocite (Cu2S), covellite (CuS), bornite (Cu5FeS4), tetrahedrite ((Cu,Fe)12Sb4S13) and enargite (Cu3AsS4). The largest source of copper is from porphyry ore deposits in which one or a combination of the minerals occurs. A typical copper sulphide ore contains various levels of iron sulphide types that generally include pyrite (FeS2) and pyrrhotite (Fe1-xS). Often gold and silver are present which may either be associated with the sulphides or are free. The gangue particles can consist of a range of silicate minerals from quartz to talc and clays. Item Specification CR2O3: 42% Basis: 40% Min CR/FE Ratio: 1.35:1 MGO: 14% Max AL2O3: 16% Max SIO2: 10% Max P: 0.01% Max S: 0.01% Max Size 0-2 MM: (95% Min) Moisture at 105C or 110C: 8% Max