• journal_title：Mineralogical Magazine
• Contributor：I. V. Pekov ; N. V. Zubkova ; M. E. Zelenski ; V. O. Yapaskurt ; Yu. S. Polekhovsky ; O. A. Fadeeva ; D. Yu. Pushcharovsky
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2013.077.1.10
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：77
• issue：1
• firstpage：107
• section：Letter

A new mineral, yaroshevskite, ideally Cu₉O₂(VO₄)₄Cl₂, occurs in sublimates collected from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, hematite, tenorite, lyonsite, melanothallite, atlasovite, kamchatkite and secondary avdoninite, belloite and chalcanthite. Yaroshevskite forms isolated prismatic crystals, up to 0.1 × 0.15 × 0.3 mm in size, on the surface of euchlorine crusts. The mineral is opaque and black, with a reddish black streak and lustre between metallic and adamantine. Yaroshevskite is brittle, no cleavage was observed and the fracture is uneven. The Mohs hardness is ~3½ (corresponding to a mean VHN micro-indentation hardness of 172 kg mm⁻²) and the calculated density is 4.26 g cm⁻³. In reflected light, yaroshevskite is grey with a weak bluish hue. Pleochroism, internal reflections and bireflectance were not observed. Anisotropy is very weak. The composition (wt.%) determined by electron microprobe is: CuO 61.82, ZnO 0.53, Fe₂O₃ 0.04, V₂O₅ 31.07, As₂O₅ 0.32, MoO₃ 1.56, Cl 6.23, O=Cl₂ −1.41; total 100.16. The empirical formula, calculated on the basis of 20 (O + Cl) anions is (Cu_8.80Zn_0.07Fe_0.01)_Σ8.88 (V_3.87Mo_0.12As_0.03)_Σ4.02O_18.01Cl_1.99. Yaroshevskite is triclinic, space group P1İ, a = 6.4344(11), b = 8.3232(13), c = 9.1726(16) Å, α = 105.338(14), β = 96.113(14), γ = 107.642(1)°, V = 442.05(13) ų and Z = 1. The nine strongest reflections in the X-ray powder pattern [d_obs in Å(I)(hkl)] are as follows: 8.65(100)(001); 6.84(83)(01İ1); 6.01(75)(100); 5.52(60)(1İ01); 4.965(55)(011); 4.198(67)(1İ1İ1); 4.055(65)(110); 3.120(55)(021); 2.896(60)(21İ1,003,2İ20). The crystal structure was solved by direct methods from single-crystal X-ray diffraction data and refined to R = 0.0737. The yaroshevskite structure is unique. It is based on corrugated layers made up of chains of edge-sharing flat squares with central Cu²⁺ cations [Cu(1), Cu(4) and Cu(5)]; neighbouring chains are connected via groups consisting of three Cu²⁺-centred squares [two Cu(3) and Cu(6)]. Neighbouring layers are connected via pairs of Cu(2)O₄Cl five-coordinate polyhedra and isolated VO₄ tetrahedra. The structure of yaroshevskite can also be considered in terms of oxygen-centred tetrahedra: O(7)Cu₄ tetrahedra are connected via common Cu(4) and Cu(5) vertices to form pyroxene-like chains [O₂Cu₆]^∞. In this context, the structural formula can be written Cu₃[O₂Cu₆][VO₄]₄Cl₂. The mineral name honours the Russian geochemist Alexei A. Yaroshevsky (b. 1934) of Moscow State University.