Vasilseverginite
A very rare copper oxo-arsenate-sulfate of novel structure, from Tolbachik's fumaroles.
Intro adapted from Wikipedia (CC BY-SA).
Vasilseverginite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₉O₄(AsO₄)₂(SO₄)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: specific gravity 4.409; Light green streak; Vitreous luster; optically biaxial.
IMA symbol Vas, IMA status: approved, named in 2015.
A volcanic sublimate on basaltic scoria in the walls of a fumarole at temperatures higher than 380 flC.
It is found associated with Tenorite, lammerite, lammerite-β, stranskiite, langbeinite, dolerophanite, hematite, As-bearing sanidine, Cu-bearing gahnite (specimen 1); johillerite.
The mineral was named to honor Russian mineralogist, geologist, and chemist Vasiliy Mikhailovich Severgin (1765- 1826), Academician of the Russian Academy of Sciences.