Aleutite [Cu₅O₂](AsO₄)(VO₄)·(Cu_0.5□_0.5)Cl, a new complex salt-inclusion mineral with Cu²⁺substructure derived from a Kagome-net

Abstract

Abstract Aleutite, ideally [Cu 5 O 2 ](AsO 4 )(VO 4 )·(Cu 0.5 □ 0.5 )Cl, was found in the Yadovitaya fumarole of the Second scoria cone of the Great Fissure Tolbachik eruption, Kamchatka Peninsula, Russia. Aleutite occurs as individual crystals in the masses of polycrystalline anhydrite. Aleutite is monoclinic, C 2 /m , a = 18.090(2) Å, b = 6.2284(6) Å, c = 8.2465(9) Å, β = 90.597(2)°, V = 929.1(2) Å 3 and Z = 4 (from single-crystal X-ray diffraction data). The empirical formula calculated on the basis of (As + V+Mo + Fe 3+ ) = 2 atoms per formula unit is Сu 5.40 Zn 0.05 Ca 0.01 As 1.09 V 0.84 Mo 0.04 Fe 0.03 K 0.05 Pb 0.02 Rb 0.01 Cs 0.01 O 9.97 Cl 1.07 . The crystal structure was solved by direct methods and refined to an agreement index R 1 = 0.066. Aleutite has a new structure type. Aleutite is unique amongst natural and synthetic copper vanadates and arsenates, as it has As 5+ and V 5+ cations ordered over two tetrahedral sites. The topology of ${}_\infty ^1 [{\rm Cu_5O_2}]^{6 +} $ oxocentred bands in aleutite is novel and has not been described before in minerals and synthetic materials. The structural architecture of the ${}_\infty ^1 [{\rm Cu_5O_2}]^{6 +} $ band in aleutite can be derived from a kagome network and represents a one-dimensional slice from it. In addition, aleutite is an interesting and complex example of a natural salt-inclusion phase.