Ullmannite and Heyrovskyite veins of the Genevskaya Darasunskoye gold deposit in Eastern Transbaikalia (Russia)

Abstract

The first data on the mineral composition of the vein of the Geneva Darasunskoye gold deposit in Transbaikalia are given. Particular attention is paid to the rare mineral ulmannite NiSbS, which has not been described before, and Heyrovskyite, which is previously unknown in the ores of this deposit, which belongs to rare minerals of the lead-bismuth sulfosal salt group. Both mineral species are found in propylites containing a gold-bearing vein. Among the ulmannites, arsenic and non-arsenic varieties were found. The arsenic content is in the range of 4.9 – 7.37 wt.%. Two of the analyzed samples contained copper contents of 0.83–0.87 wt. %. All measured individuals contain iron ranging from 0.57 to 1.75 wt.% and there is a sulfur deficiency. For the first time, a lead-silver-bismuth sulfosalt belonging to heyrovskite was identified in the near-salband part of the Geneva gold-bearing vein of the Darasun gold deposit. Its composition is not constant. Kheyrovskite of the Darasun deposit differs in chemical composition from its other known occurrences in its relatively high antimony content up to 2.12%, as well as a high bismuth content and sulfur deficiency. Both minerals belong to the early stage of the formation of the Geneva gold vein.