Tillmannsite, (Ag₃Hg)(V,As)O₄, a new mineral: its description and crystal structure

Authors: Sarp, Halil; Pushcharovsky, Dmitry Y.u.; MacLean, Elizabeth J.; Teat, Simon J.; Zubkova, Natalia V.

Source: European Journal of Mineralogy, Volume 15, Number 1, 1 February 2003 , pp. 177-180(4)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

Tillmannsite, (Ag₃Hg)(V,As)O₄, was found in the old copper mines of Roua (Alpes-Maritimes, France), associated with pecoraite, vésigniéite, olivenite, kolfanite, janggunite, chlorargyrite, cuprite, native copper, native silver, native silver containing 2 % of mercury, domeykite, djurleite and algodonite. It forms aggregates (0.2 mm diameter) consisting of pseudooctahedral crystals (50μm maximum dimension). The crystals are red, brownish red. The mineral is tetragonal, I4, a = 7.727(7) Å, c = 4.648(5) Å, V = 277.5(5) Å³, Z = 2 and D_calc = 7.733(3) g/cm³. The strongest lines in the X-ray powder diffraction pattern (d_obs in Å, (hkl), I_vis) are: 5.45, (110), 25; 2.772, (211), 100; 2.324, (002), 30; 2.254, (301), 20. Luster is adamantine translucent, streak is brownish red; crystals are uniaxial (+) with ω - 2.3, ε - 2.5 at 589 nm. Pleochroism is intense with ε = red orange intense, ω = orange brown. The crystal structure was solved from data collected using synchrotron radiation by traditional direct methods and refined using 350 observed unique reflections to R(F) = 0.037, Rw(F²) = 0.075. The structure of tillmannsite containes isolated tetrahedra (V,As)O₄ and tetrahedral clusters (Ag₃Hg) formed by metallic atoms. Each (Ag,Hg) metallic atom is coordinated by 3 metallic neighbors and by 3 oxygens.

Keywords: TILLMANNSITE; CRYSTAL STRUCTURE; VANADATE; SILVER; MERCURY; ROUA FRANCE

Document Type: Research article

DOI: http://dx.doi.org/10.1127/0935-1221/2003/0015-0177

Publication date: 2003-02-01

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