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The crystal structure (R = 0.0194) of arcanite β-K2SO4 was studied on a single crystal from exhalations of the Arsenatnaya fumarole, Tolbachik Volcano (Kamchatka, Russia). The mineral crystallizes at a temperature of ≥350-430°C and associates with langbeinite, aphthitalite, hematite, tenorite, johillerite, and others. Arcanite is orthorhombic, Pnma, a = 7.4763(2) Å, b = 5.77262(16) Å, c = 10.0630(3) Å, V = 434.30(2) Å3, Z = 4. Its structure contains isolated SO4 tetrahedra, whereas K cations center ten- and nine-fold polyhedra. [ABSTRACT FROM AUTHOR]

The new mineral pharmazincite, KZnAsO4, 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 closely associated with shchurovskyite, dmisokolovite, bradaczekite, arsmirandite, tilasite, johillerite, tenorite, hematite, aphthitalite and As-bearing orthoclase. Pharmazincite occurs as prismatic to acicular crystals up to 1 mmlong and up to 0.03 mmthick typically combined in near-parallel, radial or chaotic intergrowths, open-work aggregates or crusts up to 2 mm across. Pharmazincite is colourless to white, transparent, with a vitreous lustre. It is brittle, with a stepped fracture and a perfect cleavage parallel to [001]. Dcalc is 4.75 g cm-3. Pharmazincite is optically uniaxial (-), ω = 1.649(2), ε = 1.642(2). The Raman spectrum is reported. The chemical composition (wt.%, electron-microprobe data) is: K2O 18.98, CaO 0.14, MgO 1.20, CuO 4.41, ZnO 27.58, Fe2O3 0.15, P2O5 0.50, As2O5 46.67, total 99.63. The empirical formula, calculated based on 4 O apfu, is: (K0.97Ca0.01)Σ0.98(Zn0.82Cu0.13Mg0.07Fe3+0.01)Σ1.03(As0.98P0.02)Σ1.00O4. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I )(hkl)] are: 6.36 (28)(111), 4.64(45)(220), 4.35(48)(002), 3.260(36)(411), 3.179(100)(222), 2.770(26)(113), 2.676(77) (600), 2.278(15)(602) and 1.710(15)(713, 115). Pharmazincite is hexagonal, a = 18.501(4), c = 8.7114(9) Å, V = 2582.4(8) Å3 and Z = 24 (single-crystal XRD data). Its space group is P63, by analogy with synthetic KZnAsO4 that has a crystal structure based upon a tetrahedral tridymite-type {ZnAsO4}- framework. It is isostructural with megakalsilite KAlSiO4. The new mineral is named for its chemical constituents. [ABSTRACT FROM AUTHOR]

The new mineral melanarsite, K3Cu7Fe3+O4(AsO4)4, was found in the sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. It is associated with dmisokolovite, shchurovskyite, bradaczekite, hematite, tenorite, aphthitalite, johillerite, arsmirandite, As-bearing orthoclase, hatertite, pharmazincite, etc. Melanarsite occurs as tabular to prismatic crystals up to 0.4 mm, separate or combined in clusters up to 1 mm across or in interrupted crusts up to 0.02 cm × 1 cm × 1 cm covering basalt scoria. The mineral is opaque, black, with a vitreous lustre. Melanarsite is brittle. Mohs' hardness is ∼4 and the mean VHN = 203 kg mm-2. Cleavage was not observed and the fracture is uneven. Dcalc is 4.39 g cm-3. In reflected light, melanarsite is dark grey. Bireflectance is weak, anisotropism is very weak. Reflectance values [R1-R2, % (λ, nm)] are 10.5-9.4 (470), 10.0-8.9 (546), 9.7-8.7 (589), 9.5-8.6 (650). The Raman spectrum is reported. Chemical composition (wt.%, electron microprobe) is K2O 10.70, CaO 0.03, CuO 45.11, ZnO 0.24, Al2O3 0.32, Fe2O3 6.11, TiO2 0.12, P2O5 0.07, As2O5 36.86, total 99.56. The empirical formula, based on 20 O apfu, is (K2.81Ca0.01)Σ2.82(Cu7.02 Al0.08Zn0.04Ti0.02)Σ8.11(As3.97P0.01)Σ3.98O20. Melanarsite is monoclinic, C2/c, a = 11.4763(9), b = 16.620(2), c = 10.1322(8) Å, β = 105.078(9)°, V = 1866.0(3) ų and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 9.22(100)(110), 7.59(35)(11), 6.084(17)(111), 4.595(26)(31, 220, 21), 3.124(22)(31, 51), 2.763(20)(400, 52), 2.570(23)(043) and 2.473(16)(260, 61, 350). Melanarsite has a novel structure type. Its crystal structure, solved from single-crystal X-ray diffraction data (R = 0.091), is based upon a heteropolyhedral pseudo-framework built by distorted Cu(1-3)O6 and (Fe,Cu)O6 octahedra and As(1-3)O4 tetrahedra. Two crystallographically independent K+ cations are located in the tunnels and voids of the pseudo-framework centring eight- and seven-fold polyhedra. The name reflects the mineral being an arsenate and its black colour (from the Greek μέλαν, black). [ABSTRACT FROM AUTHOR]

A new mineral katiarsite, ideally KTiO(AsO4), occurs 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 with hatertite, bradaczekite, johillerite, yurmarinite, tilasite, arsmirandite, hematite, tenorite, As-bearing orthoclase, fluorophlogopite and aphthitalite. Katiarsite occurs as long prismatic to acicular, typically sword-like, crystals up to 3 μm?10 μm?50 μmin size, and rarely up to 0.15 mm long. Crystal forms are {011}, {201}, {100} and {001}. Katiarsite is transparent, colourless, with a vitreous lustre. The mineral is brittle. Cleavage was not observed, the fracture is uneven. Dcalc is 3.49 g cm-3. Katiarsite is optically biaxial (+), α = 1.784(3), β = 1.792(3), γ = 1.870(5); 2Vobs is small. Orientation is X=b, Y = a, Z = c. The Raman spectrum is reported. The chemical composition (wt.%, electron-microprobe data) is K2O 18.98, Fe2O3 5.07, TiO2 27.49, As2O5 47.48, total 99.02. The empirical formula, calculated based on 5 O apfu, is K1.00(Ti0.85Fe0.16 3+)S1.01As1.02O5. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I )(hkl)] are 5.91(17)(110), 5.62(74)(011), 4.18(19)(202), 3.157(66) (013), 2.826(100)(221), 2.809(96)(022) and 2.704(19)(004). Katiarsite is orthorhombic, a = 13.174(4), b = 6.5635(10), c = 10.805(2) Å, V = 934.3(3) ų, Z = 8, space group Pna21, by analogy with KTA, synthetic KTiO(AsO4), a notable non-linear optical crystalline material. The name of the mineral reflects its chemical composition, kalium titanyl arsenate. [ABSTRACT FROM AUTHOR]

A new mineral chrysothallite K6Cu6Tl3+Cl17(OH)4·H2O was found in two active fumaroles, Glavnaya Tenoritovaya and Pyatno, at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Chrysothallite seems to be a product of the interactions involving high-temperature sublimate minerals, fumarolic gas and atmospheric water vapour at temperatures not higher than 150ºC. It is associated with belloite, avdoninite, chlorothionite, sanguite, eriochalcite, mitscherlichite, sylvite, carnallite and kainite at Glavnaya Tenoritovaya and with belloite, avdoninite, chlorothionite, eriochalcite, atacamite, halite, kröhnkite, natrochalcite, gypsum and antlerite at Pyatno. The mineral forms equant-to-thick tabular crystals up to 0.05 mm, typically combined in clusters or crusts up to 1 mm across. Crystal forms are: {001}, {100}, {110}, {101} and {102}. Chrysothallite is transparent, bright golden-yellow to light yellow in finely crystalline aggregates. The lustre is vitreous. The mineral is brittle. Cleavage was not observed, the fracture is uneven. Dmeas= 2.95(2), Dcalc= 2.97 g cm–3. Chrysothallite is optically uniaxial (+), ω = 1.720(5), = 1.732(5). The Raman spectrum is given. The chemical composition (wt.%, electron-microprobe data, H2O calculated based on the crystal structure data) is: K 15.92, Cu 24.56, Zn 1.38, Tl 13.28, Cl 40.32, H2O(calc.) 3.49, total 98.95. The empirical formula, calculated on the basis of 17 Cl + 5 O a.p.f.u., is: K6.09(Cu5.78Zn0.32)Σ6.10Tl0.97Cl17[(OH)3.80O0.20]·H2O. Chrysothallite is tetragonal, I4/mmm, a= 11.3689(7), c= 26.207(2) Å, V= 3387.3(4) Å3, Z= 4. The strongest reflections of the powder X-ray pattern [d, Å (I)(hkl)] are: 13.20(44)(002); 6.88(100)(112); 5.16(30)(202, 114); 4.027(25)(220); 3.471(28)(206), 3.153(30)(314), 3.075(47)(305), 2.771(38)(316). The crystal structure (solved from single-crystal X-ray diffraction data, R= 0.0898) is unique. Its basic structural unit is a (001) layer of edge-sharing distorted CuCl4(OH)2octahedra. Two Tl3+cations occupy the centre of isolated TlCl6and TlCl4(H2O)2octahedra connected to each other and to the Cu polyhedral layers viaKCl6and KCl9polyhedra. The name reflects the bright golden-yellow colour of the mineral (from the Greek χρσ, gold) and the presence of thallium. Chrysothallite is the second known mineral with species-defining trivalent thallium. [ABSTRACT FROM AUTHOR]

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-β, 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 ∼3½. Ericlaxmanite is green to dark green. Kozyrevskite is bright grass green to light yellowish green; Dcalcis 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)° kozyrevskite: α = 1.885(8), β = 1.895(8), γ = 1.900(8), 2Vmeas.= 75(10)°. 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; Fe2O30.26, 0.12; SiO2n.d., 0.12; P2O50.23, 1.23; V2O50.14, 0.37; As2O540.57, 38.78; SO30.17, 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)Σ1.98O9and kozyrevskite: (Cu3.95Zn0.07Fe0.01)Σ4.03(As1.83P0.09S0.03V0.02Si0.01)Σ1.98O9. Ericlaxmanite is triclinic, P1, 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)°, V= 361.11(3) Å3and Z= 2. Kozyrevskite is orthorhombic, Pnma, a= 8.2581(4), b= 6.4026(4), c= 13.8047(12) Å, V= 729.90(9) Å3and Z= 4. The strongest reflections in the X-ray powder patterns [dÅ (I)(hkl)] are: ericlaxmanite: 3.868(46)(101), 3.685(100)(020), 3.063(71)(012), 2.957(58)(022), 2.777(98)(212, 211), 2.698(46)(212) 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. [ABSTRACT FROM AUTHOR]