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

Abstract

The new mineral zubkovaite, Ca3Cu3(AsO4)4, was found in 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 with anhydrite, svabite, hematite, johillerite, tilasite, fluorophlogopite, sanidine and aphthitalite. Zubkovaite occurs as coarse prismatic crystals up to 0.01 mm × 0.01 mm × 0.2 mm combined in radiating aggregates or crusts. The mineral is transparent, bright sky-blue, turquoise-coloured or light bluish-green, with vitreous lustre. It is brittle, with imperfect cleavage. The Mohs’ hardness is ca 3. Dcalc is 4.161 g cm–3. Zubkovaite is optically biaxial (–), α = 1.747(5), β = 1.774(5), γ = 1.792(5) and 2Vmeas = 75(10)°. Chemical composition (wt.%, electron microprobe) is: CaO 19.22, CuO 27.37, As2O5 52.54, SO3 0.67, total 99.80. The empirical formula based on 16 O apfu is Ca2.96Cu2.97(As3.945S0.07)Σ4.015O16. Zubkovaite is monoclinic, C2, a = 16.836(3), b = 5.0405(8), c = 9.1173(17) Å, β = 117.388(13)°, V = 687.0(2) Å3 and Z = 2. The strongest reflections of the powder XRD pattern [d,Å (I) (hkl)] are: 7.44 (100) ($\bar 2$01), 3.727 (79) (400, $\bar 2$02, $\bar 3$11), 3.334 (92) ($\bar 1$12), 2.914 (73) (311), 2.765 (50) ($\bar 6$01, $\bar 6$02), 2.591 (96) ($\bar 3$13) and 2.521 (53) (020). The crystal structure is unique for minerals. It was solved from single-crystal X-ray diffraction data to R = 7.19%. The structure contains trimers of Cu2+-centred polyhedra (consisting of one distorted square CuO4 in the core and two distorted square pyramids CuO5) and two crystallographically independent As5+O4 tetrahedra playing different roles: As(2)O4 tetrahedra link neighbouring trimers into ribbons whereas As(1)O4 tetrahedra link adjacent ribbons into heteropolyhedral layers; Ca cations are located in the interlayer space. The mineral is named in honour of the Russian crystallographer and crystal chemist Natalia Vital'evna Zubkova (born 1976).

Antofagastaite, Na2Ca(SO4)2·1.5H2O, a new mineral related to syngenite

“…4) and blödite. An earlier, high-temperature assemblage of sublimate minerals include: hematite, anhydrite, aphthitalite, fluorophlogopite, sanidine (As-bearing), johillerite, svabite, tilasite and zubkovaite Ca 3 Cu 3 (AsO 4 ) 4 (IMA2018-008, Pekov et al, 2019).

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New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XV. Calciojohillerite, NaCaMgMg2(AsO4)3, a member of the alluaudite group

“…One of the outstanding features of this fumarole is the abundance of new arsenate minerals (Pekov et al , 2018a). Seventeen new species were characterised in the previous articles of this series, namely yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al , 2014a), two polymorphs of Cu 4 O(AsO 4 ) 2 , ericlaxmanite and kozyrevskite (Pekov et al , 2014b), popovite Cu 5 O 2 (AsO 4 ) 2 (Pekov et al , 2015a), 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 , 2015b), katiarsite KTiO(AsO 4 ) (Pekov et al , 2016a), melanarsite K 3 Cu 7 Fe 3+ O 4 (AsO 4 ) 4 (Pekov et al , 2016b), pharmazincite KZnAsO 4 (Pekov et al , 2017), arsenowagnerite Mg 2 (AsO 4 )F (Pekov et al , 2018b), arsenatrotitanite NaTiO(AsO 4 ) (Pekov et al , 2019a), the two 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 , 2019b), anatolyite Na 6 (Ca,Na)(Mg,Fe 3+ ) 3 Al(AsO 4 ) 6 (Pekov et al , 2019c), zubkovaite Ca 3 Cu 3 (AsO 4 ) 4 (Pekov et al , 2019d), pansnerite K 3 Na 3 Fe 3+ 6 (AsO 4 ) 8 (Pekov et al , 2020a) and badalovite NaNaMg(MgFe 3+ )(AsO 4 ) 3 (Pekov et al , 2020b). The latter belongs to the alluaudite group, a subdivision of the alluaudite supergroup, as well as the new mineral calciojohillerite described in the present paper.…”

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XIV. Badalovite, NaNaMg(MgFe3+)(AsO4)3, a member of the alluaudite group

“…This paper continues the 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 1975–1976, Tolbachik volcano, Kamchatka Peninsula, Far-Eastern Region, Russia (55°41′N, 160°14′E, 1200 m asl). Sixteen new species have been characterised in previous articles in the series: yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al ., 2014a), two polymorphs of Cu 4 O(AsO 4 ) 2 , ericlaxmanite and kozyrevskite (Pekov et al ., 2014b), popovite Cu 5 O 2 (AsO 4 ) 2 (Pekov et al ., 2015a), 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 ., 2015b), katiarsite KTiO(AsO 4 ) (Pekov et al ., 2016b), melanarsite K 3 Cu 7 Fe 3+ O 4 (AsO 4 ) 4 (Pekov et al ., 2016c), pharmazincite KZnAsO 4 (Pekov et al ., 2017), arsenowagnerite Mg 2 (AsO 4 )F (Pekov et al ., 2018b), arsenatrotitanite NaTiO(AsO 4 ) (Pekov et al ., 2019a), the two 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 ., 2019b), anatolyite Na 6 (Ca,Na)(Mg,Fe 3+ ) 3 Al(AsO 4 ) 6 (Pekov et al ., 2019c), zubkovaite Ca 3 Cu 3 (AsO 4 ) 4 (Pekov et al ., 2019d) and pansnerite K 3 Na 3 Fe 3+ 6 (AsO 4 ) 8 (Pekov et al ., 2020).…”