Germanocolusite, Colusite and Stibiocolusite from Calcite-Sphalerite Veins of the Koshka Carbonatite Massif, Eastern Taimyr

For the first time on the Taimyr Peninsula, germanium mineralization, including its own mineral phases — minerals of the germanite group, namely germanocolusite, colusite and stibiocolusite, has been found and described. These minerals were discovered in calcite-sphalerite veins of the Koshka carbonatite massif, which belongs to the Middle-Late Triassic volcano-plutonic carbonate belt of the Taimyr Peninsula. In this members of the germanite group variations in the composition in the ratios of Ge, As, Sb and Sn are wide. Members of the colusite–germanocolusite isomorphous series are common whereas stibiocolusite is rare. These minerals form zonal crystals 5–50 µm in size in association with complex zonal sphalerite, chalcopyrite, pyrite, and less common galena. Colusite crystals exhibit both zoning with enrichment of the marginal parts by Sb and Sn, and oscillatory zoning, with rhytmic varying of the contents of many species-defining components. Germanocolusite contains up to 11 wt. % Ge (5.1 apfu Ge); colusite – up to 11.5 wt. % As (5.99 apfu As); stibiocolusite – up to 6.9 wt. % Sb (1.92 apfu Sb); the Sn content does not exceed 4.1 wt. % (1.19 apfu Sn). Reflectance spectra and unit-cell parameter of these minerals were also determined.

colusite, germanocolusite, stibiocolusite, Koshka carbonatite massif, Eastern Taimyr