Parapierrotite from the Vorontsovskoe gold deposit, Northem Urals, Russia: crystal structure and chemical composition

Plâsil J., Kasatkin A. V., Skoda R., Stepanov S. Yu.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 1. P. 68-78

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Language: English

Abstract

We report data on the chemical composition and crystal structure of parapierrotite, TlSb₅S₈, recently found at the Vorontsovskoe gold deposit (Sverdlovskaya Oblast’, Northern Urals, Russia). It forms there short prismatic crystals up to 1 mm across embedded in a calcite-quartz matrix in association with orpiment, prehnite and baryte. Electron microprobe analysis yields the empirical formula (calculated on the basis of sum of 14 atoms) Tl_1.01(Sb_4.75As_0.28)S_5.03S_7.95. Crystal structure of parapierrotite was solved at the first time. It is determined from single-crystal X-ray diffraction data and refined to R = 0.0536 for 4643 observed reflections with I > 3(σ). Parapierrotite is monoclinic, space group Pn, with unit-cell parameters a = 8.0832(5), b = 19.4057(11), c = 9.0465(5) Å, β = 91.908(6)°, V = 1418.25(1) ų and Z = 4. The structure of parapierrotite is identical to previously reported structure of synthetic TlSb₅S₈.

Key words: parapierrotite, synthetic TlSb₅S₈, As admixture, Vorontsovskoe gold ore deposit, the Urals.