The mineralogy and mineral chemistry of indium in sulphide deposits and implications for mineral processing

Understanding of the metallurgical behaviour of indium is dependent on an accurate appraisal of the mineralogical site of the element in a given ore or concentrate. The dominant indium-bearing mineral in (Pb)–Zn ores and concentrates is sphalerite. Indium is substituted within the crystal lattice of sphalerite via the coupled substitution 2Zn2+ ↔ Cu+ + In3+, typically at concentrations ranging from < 1 ppm up to several wt.%. Chalcopyrite may play a subordinate role as an indium-carrier, but is only important when there is little sphalerite present. Discrete indium-minerals such as roquesite (CuInS2) or laforêtite (AgInS2) are generally only minor phases, except in indium-bearing ores with extremely low Zn content. Minor amounts of indium may also be incorporated into other phases such as stannite or stannoidite, but these minerals are likely to play a negligible role in the overall mineralogical balance for indium.