New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. VIII. Arsenowagnerite, Mg₂(AsO₄)F

Abstract

A new mineral arsenowagnerite, Mg2(AsO4)F, the arsenate analogue of wagnerite, was found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated closely with johillerite, tilasite, anhydrite, hematite, fluorophlogopite, cassiterite, calciojohillerite, aphthitalite and fluoborite. Arsenowagnerite occurs as equant to tabular crystals up to 1 mm across combined in interrupted crusts up to 0.1 cm × 1.5 cm × 3 cm. The mineral is transparent, light yellow, lemon-yellow, greenish-yellow or colourless and has a vitreous lustre. Arsenowagnerite is brittle, with Mohs hardness of ~5. Cleavage is distinct, the fracture is uneven. Dcalc = 3.70 g cm–3. Arsenowagnerite is optically biaxial (+), α = 1.614(2), β = 1.615(2), γ = 1.640(2) and 2Vmeas = 25(5)°. Wavenumbers of the strongest absorption bands in the IR spectrum (cm–1) are: 874, 861, 507, 491 and 470. The chemical composition (average of six electron-microprobe analyses, wt.%) is: MgO 38.72, CaO 0.23, MnO 0.32, CuO 0.60, ZnO 0.05, Fe2O3 0.11, TiO2 0.03, SiO2 0.08, P2O5 0.18, V2O5 0.03, As2O5 54.96, SO3 0.10, F 8.91 and –O=F –3.75, total 100.57. The empirical formula calculated on the basis of 5 (O + F) apfu is: (Mg1.98Cu0.02Mn0.01Ca0.01)Σ2.02(As0.99P0.01)Σ1.00O4.03F0.97. Arsenowagnerite is monoclinic, P21/c, a = 9.8638(3), b = 12.9830(3), c = 12.3284(3) Å, β = 109.291(3)°, V = 1490.15(7) Å3 and Z = 16. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 5.80(41)(002), 5.31(35)(120), 3.916(37)($\bar 2$21), 3.339(98)(221, 023), 3.155(65)(202), 3.043(100)($\bar 1$41), 2.940(72)($\bar 2$04), 2.879(34)($\bar 3$22) and 2.787(51)(320, $\bar 1$24). The crystal structure was solved from single-crystal X-ray diffraction data, R = 0.0485. Arsenowagnerite is isostructural to wagnerite-Ma2bc. The crystal structure is built by almost regular AsO4 tetrahedra, distorted MgO4F2 octahedra and distorted MgO4F trigonal bipyramids.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XI. Anatolyite, Na6(Ca,Na)(Mg,Fe3+)3Al(AsO4)6

“…(2014 a , 2018 a ). In particular, 13 new arsenates from this locality have been characterised: yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al ., 2014 a ), two polymorphs of Cu 4 O(AsO 4 ) 2 , ericlaxmanite and kozyrevskite (Pekov et al ., 2014 b ), popovite Cu 5 O 2 (AsO 4 ) 2 (Pekov et al ., 2015 b ), structurally related shchurovskyite K 2 CaCu 6 O 2 (AsO 4 ) 4 and dmisokolovite K 3 Cu 5 AlO 2 (AsO 4 ) 4 (Pekov et al ., 2015 c ), katiarsite KTiO(AsO 4 ) (Pekov et al ., 2016 b ), melanarsite K 3 Cu 7 Fe 3+ O 4 (AsO 4 ) 4 (Pekov et al ., 2016 c ), pharmazincite KZnAsO 4 (Pekov et al ., 2017), arsenowagnerite Mg 2 (AsO 4 )F (Pekov et al ., 2018 b ), arsenatrotitanite NaTiO(AsO 4 ) (Pekov et al ., 2019 a ), and isostructural minerals edtollite K 2 NaCu 5 Fe 3+ O 2 (AsO 4 ) 4 and alumoedtollite K 2 NaCu 5 AlO 2 (AsO 4 ) 4 (Pekov et al ., 2019 b ).…”

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XII. Zubkovaite, Ca3Cu3(AsO4)4

“…This paper is part of the series of articles containing descriptions of new arsenate minerals from the Arsenatnaya fumarole of the Tolbachik volcano at the Kamchatka Peninsula, Far-Eastern Region, Russia. Fourteen new arsenate species from this fumarole have already been characterised: yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al ., 2014 a ), two polymorphs of Cu 4 O(AsO 4 ) 2 , ericlaxmanite and kozyrevskite (Pekov et al ., 2014 b ), popovite Cu 5 O 2 (AsO 4 ) 2 (Pekov et al ., 2015 a ), structurally related shchurovskyite K 2 CaCu 6 O 2 (AsO 4 ) 4 and dmisokolovite K 3 Cu 5 AlO 2 (AsO 4 ) 4 (Pekov et al ., 2015 b ), katiarsite KTiO(AsO 4 ) (Pekov et al ., 2016 a ), melanarsite K 3 Cu 7 Fe 3+ O 4 (AsO 4 ) 4 (Pekov et al ., 2016 b ), pharmazincite KZnAsO 4 (Pekov et al ., 2017), arsenowagnerite Mg 2 (AsO 4 )F (Pekov et al ., 2018 b ), arsenatrotitanite NaTiO(AsO 4 ) (Pekov et al ., 2019 a ), pair of isostructural minerals edtollite K 2 NaCu 5 Fe 3+ O 2 (AsO 4 ) 4 and alumoedtollite K 2 NaCu 5 AlO 2 (AsO 4 ) 4 (Pekov et al ., 2019 b ), and anatolyite Na 6 (Ca,Na)(Mg,Fe 3+ ) 3 Al(AsO 4 ) 6 (Pekov et al ., 2019 c ).…”

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IX. Arsenatrotitanite, NaTiO(AsO4)

“…This paper continues a series of articles on new arsenate minerals from the Arsenatnaya fumarole located at the apical part of the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka Peninsula, Far-Eastern Region, Russia (55°41′N, 160°14′E, 1200 m asl). This active fumarole, discovered by us in July 2012, has already given rise to the new arsenates: yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al ., 2014 a ); two polymorphs of Cu 4 O(AsO 4 ) 2 , ericlaxmanite and kozyrevskite (Pekov et al ., 2014 b ); popovite Cu 5 O 2 (AsO 4 ) 2 (Pekov et al ., 2015 a ); structurally related shchurovskyite K 2 CaCu 6 O 2 (AsO 4 ) 4 and dmisokolovite K 3 Cu 5 AlO 2 (AsO 4 ) 4 (Pekov et al ., 2015 b ); katiarsite KTiO(AsO 4 ) (Pekov et al ., 2016 a ); melanarsite K 3 Cu 7 Fe 3+ O 4 (AsO 4 ) 4 (Pekov et al ., 2016 b ); pharmazincite KZnAsO 4 (Pekov et al ., 2017); and arsenowagnerite Mg 2 (AsO 4 )F (Pekov et al ., 2018 a ). The general description of this fumarole and data on the distribution of arsenate mineralisation within it are given by Pekov et al .…”