A new mineral species zincobradaczekite, NaCuCuZn2(AsO4)3, and a new isomorphous series bradaczekite–zincobradaczekite in the alluaudite group (original) (raw)

Abstract

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. D_calc is 4.71 g cm−3. Zincobradaczekite is optically biaxial (–), α 1.786(5), β 1.846(8), γ 1.90(1), 2_V_meas. 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, C_2/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)ʹCu_A(2)□A(2)ʹNa_M_(1)Cu_M_(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+.

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Acknowledgements

We thank two anonymous reviewers for their valuable comments. This work was supported by the Russian Science Foundation, Grant no. 19-17-00050. The technical support by the SPbSU X-Ray Diffraction Resource Center in the powder XRD study is acknowledged.

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Authors and Affiliations

  1. Faculty of Geology, Moscow State University, Vorobievy Gory, 119991, Moscow, Russia
    Igor V. Pekov, Natalia N. Koshlyakova, Marina F. Vigasina & Anna G. Turchkova
  2. Canadian Museum of Nature, Ottawa, ON, K1P 6P4, Canada
    Inna Lykova
  3. Fersman Mineralogical Museum of the Russian Academy of Sciences, Leninsky Prospekt 18-2, 119071, Moscow, Russia
    Dmitry I. Belakovskiy
  4. Institute of Earth Sciences, St Petersburg State University, University Embankment 7/9, 199034, St Petersburg, Russia
    Sergey N. Britvin
  5. Kola Science Center of Russian Academy of Sciences, Fersman Str. 14, 184200, Apatity, Russia
    Sergey N. Britvin
  6. Institute of Volcanology and Seismology, Far Eastern Branch of Russian Academy of Sciences, Piip Boulevard 9, 683006, Petropavlovsk-Kamchatsky, Russia
    Evgeny G. Sidorov
  7. Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14 (UZA 2), 1090, Vienna, Austria
    Katharina S. Scheidl

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  1. Igor V. Pekov
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  2. Inna Lykova
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  3. Natalia N. Koshlyakova
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  4. Dmitry I. Belakovskiy
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  5. Marina F. Vigasina
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  6. Anna G. Turchkova
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  7. Sergey N. Britvin
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  8. Evgeny G. Sidorov
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  9. Katharina S. Scheidl
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Correspondence toIgor V. Pekov.

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Pekov, I.V., Lykova, I., Koshlyakova, N.N. et al. A new mineral species zincobradaczekite, NaCuCuZn2(AsO4)3, and a new isomorphous series bradaczekite–zincobradaczekite in the alluaudite group.Phys Chem Minerals 47, 36 (2020). https://doi.org/10.1007/s00269-020-01104-8

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