A rare indium-bearing mineral (Zn-In-Cu-Fe sulphide) from the Stara Kamienica Schist Belt (Sudetes, SW Poland)

Abstract

A rare indium-bearing mineral from the stratiform Czerniawa Zdrój-Krobica Sn deposit in the Sudetes (NE part of the Bohemian Massif) has been recognized in the qualitative-quantitative chemical composition studies of sulphide-cassiterite samples by electron microprobe (EMPA). This indium-bearing mineral occurs in the form of separate hipautomorphic microscopic grains (diameter 5–20 μm) and as intergrowths and disseminations in chalcopyrite. Observations indicate that this phase crystallized with the main generation of chalcopyrite, sphalerite and also with a younger generation of cassiterite in the mineral succession. The chemical composition of this mineral is as follows: S – 29.38–30.77 wt.%, Zn – 29.76–34.02 wt.%, In – 17.52–19.40 wt.%, Cu – 9.05–10.75 wt.%, Fe – 7.76–8.7 wt.% and Sn – 0.03–0.1 wt.%. Its calculated chemical formula is: (Zn2.09In0.67Cu0.65Fe0.64Cd0.02)∑=4.07 and it is characterized by enrichment of Zn with simultaneous depletion in Cu and Sn relative to the ideal chemical composition of sakuraiite – the most similar mineral in terms of chemical composition. In the light of our new data, it should be considered as a yet unnamed Zn-In-Cu-Fe sulphide mineral. In addition, coexisting sulphide minerals – chalcopyrite (max. 1580 ppm of In) and sphalerite (max. 1640 ppm of In) were identified as indium carriers