Mineralogy of Precious Metals in Ores of the Biksizak Base–Metal Deposit, South Urals, Russia

Gold and silver mineralogy is studied in ores of the Biksizak base-metal deposit (South Urals, Russia). This is a skarn-related carbonate replacement mineralization typical for marginal zones of porphyry-epithermal systems. The variability of precious metals minerals is established. Native gold (fineness 853 to 939) in assemblage with chalcopyrite and sphalerite is the most abundant. A telluride assemblage (tetradymite, hessite, stützite, petzite, galena, tellurobismuthite, rucklidgeite, altaite and native gold with a fineness of 830–900) and a silver–pearceite–acanthite assemblage (acanthite/argentite, pearceite–polybasite and gold–silver alloy from native gold with fineness of 747 to native silver) are identified. It is shown the exhibited variability is controlled by decreasing the temperature and variations in the tellurium and sulfur fugacities.