Vasilseverginite

Vasilseverginite is a very rare arsenate-sulfate mineral^[3] with formula Cu₉O₄(AsO₄)₂(SO₄)₂. Its structure is of a new type.^[2] It possesses a typical feature of many minerals of its type locality, the Tolbachik volcano, namely being a salt with oxide anions. However, it is the first Tolbachik copper oxysalt that is both arsenate and sulfate.^[4] Vasilseverginite is monoclinic, with space group P2₁/n.^[3]

Vasilseverginite
General
Category	Arsenate mineral
Formula	Cu9O4(AsO4)2(SO4)2
IMA symbol	Vas[1]
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/m
Unit cell	a = 8.113(4) Å b = 9.918(4) Å c = 11.0225(5) Å; β = 110.86° (approximated)
Identification
References	[2][3]