New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. II. Ericlaxmanite and kozyrevskite, two natural modifications of Cu₄O(AsO₄)₂

Abstract

Two new minerals, ericlaxmanite and kozyrevskite, dimorphs of Cu4O(AsO4)2, were 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. They are associated with each other and with urusovite, lammerite, lammerite-b, popovite, alarsite, tenorite, hematite, aphthitalite, langbeinite, As-bearing orthoclase, etc. Ericlaxmanite occurs as tabular, lamellar, equant or short prismatic crystals up to 0.1 mm in size, their clusters and pseudomorphs after urusovite crystal crusts up to 1.5 cm × 2 cm in area. Kozyrevskite occurs as prismatic crystals up to 0.3 mm long in clusters and as individual crystals. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ~3–. Ericlaxmanite is green to dark green. Kozyrevskite is bright grass green to light yellowish green; Dcalc is 5.036 (ericlaxmanite) and 4.934 (kozyrevskite) g cm–3. Both minerals are optically biaxial (–); ericlaxmanite: α = 1.870(10), β = 1.900(10), γ = 1.915(10), 2Vmeas = 60(15)º; kozyrevskite: α = 1.885(8), β = 1.895(8), γ = 1.900(8), 2Vmeas. = 75(10)º. The Raman spectra are given. Chemical data (wt.%, electron microprobe; the first value is for ericlaxmanite, the second for kozyrevskite): CuO 57.55, 58.06; ZnO 0.90, 1.04; Fe2O3 0.26, 0.12; SiO2 n.d., 0.12; P2O5 0.23, 1.23; V2O5 0.14, 0.37; As2O5 40.57, 38.78; SO3 0.17, 0.43; total 99.82, 100.15. The empirical formulae, based on 9 O a.p.f.u., are: ericlaxmanite: (Cu3.97Zn0.06Fe0.02)Σ4.05(As1.94P0.02V0.01S0.01)Σ1.98O9 and kozyrevskite: (Cu3.95Zn0.07Fe0.01)Σ4.03(As1.83P0.09S0.03V0.02Si0.01)Σ1.98O9. Ericlaxmanite is triclinic, P1̄ , a = 6.4271(4), b = 7.6585(4), c = 8.2249(3) Å , α = 98.396(4), β = 112.420(5), γ = 98.397(5)º, V = 361.11(3) Å3 and Z = 2. Kozyrevskite is orthorhombic, Pnma, a = 8.2581(4), b = 6.4026(4), c = 13.8047(12) Å , V = 729.90(9) Å3 and Z = 4. The strongest reflections in the X-ray powder patterns [d Å (I)(hkl)] are: ericlaxmanite: 3.868(46)(101), 3.685(100)(020), 3.063(71)(012), 2.957(58)(02̄ 2), 2.777(98)(2̄ 12, 2̄ 1̄ 1), 2.698(46)(2̄1̄ 2) and 2.201(51)(013, 031); kozyrevskite: 3.455(100)(004), 3.194(72)(020, 104), 2.910(69)(022), 2.732(82)(122), 2.712(87)(301) and 2.509(92)(123). Their crystal structures, solved from single-crystal X-ray diffraction data [R = 0.0358 (ericlaxmanite) and 0.1049 (kozyrevskite)], are quite different. The ericlaxmanite structure is based on an interrupted framework built by edge- and corner-sharing Cu-centred, distorted tetragonal pyramids, trigonal bipyramids and octahedra. The kozyrevskite structure is based on complicated ribbons of Cu-centred distorted tetragonal pyramids and trigonal bipyramids. Ericlaxmanite is named in honour of the Russian mineralogist, geologist, geographer, biologist and chemist Eric Laxman (1737–1796). Kozyrevskite is named in honour of the Russian geographer, traveller and military man Ivan Petrovich Kozyrevskiy (1680–1734), one of the first researchers of Kamchatka.

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. 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 .…”

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

“…This active fumarole, discovered by us in July 2012, is described in general in the first paper devoted to yurmarinite Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 (Pekov et al ., 2014 a ). In other articles the following mineral species were characterized: 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 ) and pharmazincite KZnAsO 4 (Pekov et al ., 2017).…”