New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. II. Ericlaxmanite and kozyrevskite, two natural modifications of Cu4O(AsO4)2. (December 2014)

• Record Type: Journal Article
• Authors: Pekov, I. V.; Zubkova, N. V.; Yapaskurt, V. O.; Belakovskiy, D. I.; Vigasina, M. F.; Sidorov, E. G.; Pushcharovsky, D. Yu.
• Is Part Of: Mineralogical magazine. Volume 78:Number 7(2014)
• Page Start: 1553
• Page End: 1569
• Publication Date: 2014-12
• Subjects: ericlaxmanite, -- kozyrevskite, -- new mineral, -- copper arsenate, -- crystal structure, -- fumarolic sublimate, -- Tolbachik volcano, -- Kamchatka.; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/minmag.2014.078.7.03
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: Two new minerals, ericlaxmanite and kozyrevskite, dimorphs of Cu4 O(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; D calc 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; Fe2 O3 0.26, 0.12; SiO2 n.d., 0.12; P2 O5 0.23, 1.23; V2 O5 0.14, 0.37; As2 O5 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: (Cu3.97 Zn0.06 Fe0.02 )Σ4.05 (As1.94 P0.02 V0.01 S0.01 )Σ1.98 O9 and kozyrevskite: (Cu3.95 Zn0.07 Fe0.01 )Σ4.03 (As1.83 P0.09 S0.03 V0.02 Si0.01 )Σ1.98 O9 . 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) Å 3 and Z = 2. Kozyrevskite is orthorhombic, Pnma, a = 8.2581(4), b = 6.4026(4), c = 13.8047(12) Å, V = 729.90(9) Å 3 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.