Cranswickite — a rare tetrahydrate sulfate of magnesium MgSO₄ ∙ 4H₂O, the new find in Yakutia

Zayakina N. V.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019. V. 148. N 1. P. 49-53

https://doi.org/10.30695/zrmo/2019.1481.04

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Language: Russian 

Abstract

Cranswickite — a rare tetrahydrate magnesium sulfate, MgSO₄ ∙ 4H₂O, has been discovered in the Malo-Tarynskoe gold ore deposit in Yakutia. It is its third find in the world, the second in Yakutia. The mineral is soft, it forms a crust of white and slightly grayish color on the rock surface. It associates with mica, chlorite, quartz, gypsum and pentahydrite. Its study has been carried out by X-ray phase and electron microprobe analyses. Its chemical composition is MgO — 20.12, SO₃ — 43.50, H₂O — 36.37 wt %. The empirical crystal chemical formula of the mineral is Mg_0.99(SO₄)_1.08·4.02H₂O. The mineral is hypergenic, it is formed probably due to oxidation of pyrite in sulfidized rocks. It is sufficiently stable while stored in laboratory conditions. The photograph and X-ray diffraction pattern of the sample are given in the paper.

Key words: cranswickite, β-starkeyite, magnesium sulfates, X-ray phase, electron probe analyses,Yakutia