title: Vasilseverginite
text: # Vasilseverginite
  
  Vasilseverginite is a very rare arsenate-sulfate mineral with formula $Cu_9O_4(AsO_4)_2(SO_4)_2.$ Its structure is of a new type. 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. Vasilseverginite is monoclinic, with space group $P2_1/n.$
  
  