Dokuchaevite, ideally Cu 8 O 2 (VO 4) 3 Cl 3 , was found in a Yadovitaya fumarole of the Second scoria cone of the North Breach of the Great Tolbachik Fissure Eruption (1975-1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Dokuchaevite occurs on the crusts of various copper sulphate exhalative minerals (kamchatkite, euchlorine) as individual prismatic crystals. Dokuchaevite is triclinic, P ̅ , a = 6.332(3), b = 8.204(4), c = 15.562(8) Å, α = 90.498(8), β = 97.173(7), γ = 90.896(13)º, V = 801.9(7) Å 3 , R 1 = 0.057. The eight strongest lines of the X-ray powder diffraction pattern are (I-d-hkl): 18-15.4396-00 ̅ , 27-7.2762-0 ̅ 1, 43-5.5957-012, 33-4.8571-̅ ̅ 1, 29-3.1929-023, 30-2.7915-202, 21-2.5645-032, 100-2.5220-1 ̅ 0, 18-2.4906-130, 71-2.3267-2 ̅ 2. The chemical composition determined by electron-microprobe analysis is (wt. %): CuO 60.87, ZnO 0.50, FeO 0.36, V 2 O 5 19.85, As 2 O 5 6.96, SO 3 0.44, MoO 3 1.41, SiO 2 0.20, P 2 O 5 0.22, Cl 10.66,-O=Cl 2 2.41, total 99.06. The empirical formula calculated on the basis of 17 anions pfu is (Cu 7.72 Zn 0.06 Fe 0.05) 7.83 Crystal structure of dokuchaevite represents a new structure type with eight Cu sites, which demonstrate remarkable diversity of Cu 2+ mixed-ligand coordination environments. Crystal structure of dokuchaevite is based on OCu 4 tetrahedra that share common corners thus forming [O 2 Cu 6 ] 8+ single chains. Two of eight symmetrically independent copper atoms do not form Cu-O bonds with additional oxygen atoms, and thus are not part of the OCu 4 tetrahedra, but provide the three-dimensional integrity of the [O 2 Cu 6 ] 8+ chains into framework. TO 4 mixed tetrahedral groups are located within the cavities of the framework. The structural formula of dokuchaevite can be represented as Cu 2 [Cu 6 O 2 ](VO 4) 3 Cl 3 .