Lead–Antimony Sulfosalts from Tuscany (Italy). XXIV. Crystal Structure of Thallium-Bearing Chovanite, TlPb26(Sb,As)31S72O, from the Monte Arsiccio Mine, Apuan Alps

Minerals

GiovanniOrazio Lepore¹  Cristian Biagioni²  Natale Perchiazzi²  Nicola Demitri³  Yves Moëlo⁴ 

[1] CNR-IOM-OGG, 71 Avenue des Martyrs, F-38043 Grenoble, France;Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53, I-56126 Pisa, Italy;Elettra–Sincrotrone Trieste S.C.p.A., S.S. 14 km 163,5 in Area Science Park, Basovizza, I-34149 Trieste, Italy;Institut des Matériaux Jean Rouxel, UMR 6502, CNRS, Université de Nantes, 2, rue de la Houssinière, F-44322 Nantes CEDEX 3, France;

关键词: chovanite;    sulfosalt;    thallium;    lead;    antimony;    oxygen;    crystal structure;    Monte Arsiccio mine;    Apuan Alps;    Italy;   

DOI  :  10.3390/min8110535

来源: DOAJ

【 摘 要 】

A thallium-bearing variety of the lead⁻antimony oxysulfosalt chovanite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy) has been reexamined. It occurs as thin, ribbon-like crystals, black in color, up to 5 mm in length in vugs of dolomite ± baryte ± quartz veins embedded in the metadolostone of the Sant’Olga level. Associated minerals are rouxelite, robinsonite, sphalerite, valentinite, baryte, dolomite, quartz, and Ba-rich K-feldspar. Chemical analysis pointed to contents of Tl up to 0.86 apfu, corresponding to the ideal chemical formula TlPb₂₆(Sb,As)₃₁S₇₂O. The structural role of thallium has been investigated using single-crystal X-ray diffraction using synchrotron radiation (λ = 0.59040 Å). Thallium-rich chovanite is monoclinic, space group P2₁/c, with unit-cell parameters a = 34.280(3), b = 8.2430(7), c = 48.457(4) Å, β = 106.290(4)°, and V = 13143(2) ų. The crystal structure was refined to a final R₁ = 0.083 for 12,052 reflections with F_o > 4σ(F_o) and 1210 refined parameters. The general features of thallium-rich chovanite agree with those of chovanite. Thallium is present as Tl⁺; it is disordered among two mixed (Pb/Tl) positions, with a Tl/Pb atomic ratio below 1, that precludes this compound to be a new species.

【 授权许可】

Unknown