Vergasovaite Cu3O[(Mo,S)O-4][SO4], a new copper-oxy-molybdate-sulfate fromKamchatka

Vergasovaite occurs on encrustations of sulfates in fumaroles in the Northe rn part of the central fumarole held of cone II of the Northern Break of th e Large Tolbachik Fissure Eruption (LTFE) on the Kamchatka peninsula. It is associated with chalcocyanite, dolerophanite, euchlorine, fedotovite, teno rite, Cu-bearing anglesite and native gold. Vergasovaite has an ideal formu la Cu3O[(Mo,S)O-4][SO4]. Its space group is Pnma with a = 7.420(3), b = 6.7 41(2), c = 13.548(5) Angstrom, V = 677.6(2) Angstrom(3), and Z = 4. The fiv e strongest lines d(calc) [Angstrom] (I-calc, hkl) in the X-ray powder patt ern are: 3.096 (100, 104); 3.377 (69, 020); 2.998 (56, 121); 2.498 (54, 220 ); and 3.580 (37, 201). The olive-green mineral is transparent and distinct ly pleochroic from olive-green to a yellowish to brownish-green. Microprobe analyses revealed a partial substitution of Mo by S and minor V, leading t o the empirical formula (Cu-2.82(7),Zn-0.10(7), Pb-0.01(1))(Sigma=2.92(9))O [(Mo-0.79(7),S-0.20(5),V-0.04(3))(Sigma=1.04(3))O-4][SO4].IR spectroscopy s howed vergasovaite to be free of H2O and OH thus the mineral is a fully oxi dized mixed copper-oxy-molybdate-sulfate. Vergasovaite is isostructural wit h synthetic Cu3O[MoO4](2).