• Igor V. Pekov
  • Inna Lykova
  • Natalia N. Koshlyakova
  • Dmitry I. Belakovskiy
  • Marina F. Vigasina
  • Anna G. Turchkova
  • Sergey N. Britvin
  • Evgeny G. Sidorov
  • Katharina S. Scheidl

A new alluaudite-group mineral zincobradaczekite, a Zn–Cu ordered highly zincian analogue of bradaczekite, was discovered in sublimates of 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 bradaczekite, lammerite, lammerite-β, borisenkoite, mcbirneyite, sanidine, hematite, tenorite, pseudolyonsite, lyonsite, starovaite, rutile, tripuhyite, pseudobrookite, piypite, langbeinite, calciolangbeinite, aphthitalite, alumoklyuchevskite, and palmierite. Zincobradaczekite forms oblique-angled prismatic crystals up to 0.02 × 0.02 × 0.08 mm3 and equant or tabular crystals up to 0.05 mm. It is transparent, blue, greenish-blue, grey-blue or bluish-grey. The lustre is vitreous. Dcalc is 4.71 g cm−3. Zincobradaczekite is optically biaxial (–), α 1.786(5), β 1.846(8), γ 1.90(1), 2Vmeas. 80(5)º. Chemical composition (wt%, electron microprobe) is Na2O 4.07, K2O 0.53, CaO 0.01, MgO 0.71, MnO 0.01, CuO 19.89, ZnO 24.21, Al2O3 0.02, Fe2O3 0.90, TiO2 0.03, P2O5 0.41, V2O5 1.05, As2O5 47.10, SO3 1.01, and total 99.95. The empirical formula based on 12 O apfu is Na0.90K0.08Cu1.70Mg0.12Zn2.03Fe3+0.08(As2.79S0.09V0.08P0.04)Σ3.00O12. The simplified chemical formula is NaCu2Zn2(AsO4)3. Zincobradaczekite is monoclinic, C2/c, a 12.0375(13), b 12.4500(13), c 7.2213(8) Å, β 117.506(7)º, V 959.90(18) Å3 and Z 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are 6.21(31)(020), 3.416(70)(310, − 112), 3.200(17)(002), 2.779(23)(− 402), 2.691(100)(− 132, 240), 1.841(20)(152) and 1.680(14)(− 642). The crystal structure was solved (single-crystal XRD, R = 4.38%). The simplified crystal chemical formula is A(1)A(1)ʹCuA(2)A(2)ʹNaM(1)CuM(2)Zn2(AsO4)3 (□—vacancy) and the end-member formula is NaCuCuZn2(AsO4)3. Zincobradaczekite and bradaczekite, ideally NaCuCuCu2(AsO4)3, are isostructural. In the Yadovitaya fumarole, Mg-poor bradaczekite forms an isomorphous series with zincobradaczekite, whilst in the neighbouring Arsenatnaya fumarole only a Zn-depleted and Mg-enriched variety of bradaczekite occurs. Zincobradaczekite and bradaczekite differ from other anhydrous alluaudite-group arsenates by increased values of the c and β unit-cell parameters due to the strong Jahn–Teller distortion of M(1)O6 octahedron predominantly occupied with Cu2+.

Original languageEnglish
Article number36
Number of pages12
JournalPhysics and Chemistry of Minerals
Volume47
Issue number8
DOIs
StatePublished - 8 Aug 2020

    Research areas

  • Alluaudite group, Arsenate, Bradaczekite, Crystal structure, Fumarole, Kamchatka, New mineral, Tolbachik volcano, Zincobradaczekite, Zinc–copper substitution

    Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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