Dmitry I. Belakovskiy

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IV. Shchurovskyite, K2CaCu6O2(AsO4)4 and dmisokolovite, K3Cu5AlO2(AsO4)4

Abstract Two new minerals shchurovskyite, ideally K2CaCu6O2(AsO4)4, and dmisokolovite, ideally K3Cu5AlO2(AsO4)4, are 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 Peninsula, Russia. They are associated with one another and with johillerite, bradaczekite, tilasite, melanarsite, tenorite, hematite, aphthitalite, langbeinite, orthoclase, etc. Shchurovskyite occurs as coarse tabular or prismatic crystals up to 0.15 mm in size or anhedral grains forming parallel aggregates and crusts up to 1.5 cm × 2 cm across. Dmisokolovite forms tabular, prismatic or dipyramidal crystals up to 0.2 mm in size, commonly combined in clusters or crusts up to 0.7 cm × 1.5 cm across. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ≈ 3. Shchurovskyite is olive-green or olive drab. Dmisokolovite is bright emerald-green to light green. Dcalc = 4.28 (shchurovskyite) and 4.26 (dmisokolovite) g cm−3. Both are optically biaxial; shchurovskyite: (+), α = 1.795(5), β = 1.800(5), γ = 1.810(6), 2Vmeas = 70(15)°; dmisokolovite: (−), α = 1.758(7), β = 1.782(7), γ = 1.805(8), 2Vmeas = 85(5)°. The Raman spectra are given. Chemical data (wt.%, electron-microprobe; first value is for shchurovskyite, second for dmisokolovite):Na2O 0.00, 0.83;K2O 8.85, 10.71; Rb2O 0.11, 0.00;MgO 0.00, 0.35; CaO 4.94, 0.21; CuO 43.19, 38.67; ZnO 0.42, 0.20; Al2O3 0.04, 4.68; Fe2O3 0.00, 0.36; P2O5 0.59, 0.78; V2O5 0.01, 0.04; As2O5 40.72, 43.01; SO3 0.35, 0.00; total 99.22, 99.84. The empirical formulae, based on 18 O a.p.f.u., are shchurovskyite: K2.05Rb0.01Ca0.96Cu5.92Zn0.06Al0.01P0.09S0.05As3.86O18; dmisokolovite: Na0.28K2.36Mg0.09C a0.04Cu5.04Zn0.04 Al0.95Fe0.053+P0.11As3.88O18. The strongest reflections of X-ray powder patterns [d,Å(I)(hkl)] are shchurovskyite: 8.61(100)(200, 001), 5.400(32)(110), 2.974(32)(3̅12, 510), 2.842(47)(003, 020), 2.757(63) (6̅01, 511), 2.373(36)(512, 420) and 2.297(31)( 4̅21, 2̅22, 313); dmisokolovite: 8.34(95)(002), 5.433(84)(110), 2.921(66)(510, 3̅14), 2.853(58)(511, 020) and 2.733(100)(006, 512, 6̅02). Shchurovskyite is monoclinic, C2, a = 17.2856(9), b = 5.6705(4), c = 8.5734(6) Å, β = 92.953(6)°, V = 839.24(9) Å3 and Z = 2. Dmisokolovite is monoclinic, C2/c, a = 17.0848(12), b = 5.7188(4), c = 16.5332(12) Å, β = 91.716(6)°, V = 1614.7(2) Å3 and Z = 4. Their crystal structures [single-crystal X-ray diffraction data, R = 0.0746 (shchurovskyite) and 0.1345 (dmisokolovite: model)] are closely related in the topology of the main building units. They are based on a quasi-framework consisting of AsO4 tetrahedra and polyhedra centred by Cu in shchurovskyite or by Cu and Al in dmisokolovite. K and Ca are located in channels of the quasi-framework. The minerals are named in honour of outstanding Russian geologists and mineralogists Grigory Efimovich Shchurovsky (1803−1884) and Dmitry Ivanovich Sokolov (1788-1852).

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. III. Popovite, Cu5O2(AsO4)2

Abstract The new mineral popovite, Cu5O2(AsO4)2, 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, Russia. It is associated with ericlaxmanite, kozyrevskite, urusovite, lammerite, lammerite-b, johillerite, bradaczekite, tenorite, hematite, aphthitalite, anhydrite, langbeinite, calciolangbeinite, As-bearing orthoclase, etc. Popovite occurs as prismatic or tabular crystals and as grains up to 0.2 mm in size forming clusters up to 1.5 mm in size and as crusts on basalt scoria or on aphthitalite incrustations. Popovite is transparent with a vitreous to greasy lustre. Its colour is olive green to dark olive-green, but fine-grained varieties are light yellow-green. The mineral is brittle, with Mohs’ hardness ~3 ½. Cleavage was not observed and the fracture is uneven. Dcalc is 5.30 g cm-3. Popovite is optically biaxial (+), α = 1.84(1), β ≈ 1.86, γ = 1.96(1), 2Vmeas = 50(20)°. The Raman spectrum is given. Chemical data (wt.%, electron-microprobe) are CuO 63.28, ZnO 0.56, V2O5 0.12, As2O5 35.80, SO3 0.27, total 100.03. The empirical formula, based on 10 O a.p.f.u., is (Cu4.99Zn0.04)S5.03(As1.95S0.02V0.01)S1.98O10. Popovite is triclinic, P1̄, a = 5.1450(3), b = 6.2557(3), c = 6.2766(4) Å, α = 100.064(5), β = 96.351(5), γ = 95.100(5)°, V = 196.47(1) Å3 and Z = 1. The strongest reflections in the powder X-ray diffraction pattern [d,Å (I)(hkl)] are 3.715(36)(110, 101), 3.465(43)(11̄1), 2.968(90)(01̄2), 2.927(100)(111), 2.782(31)(1̄02), 2.768(67)(1̄20), 2.513(55)(1̄2̄1) and 2.462(67)(2̄01). Popovite has a novel structure type. Its crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0459), is based on (010) layers forming an interrupted framework. The layer consists of Cu(1)O6 octahedra with very strong Jahn-Teller distortion and Cu(2)O5 and Cu(3)O5 polyhedra. The linkage between the layers is reinforced by isolated AsO4 tetrahedra. Popovite is named in honour of the Russian mineralogists Vladimir Anatol’evich Popov (b. 1941) and Valentina Ivanovna Popova (b. 1941), a husband and wife research team working in the Institute of Mineralogy of the Urals Branch of the Russian Academy of Sciences, Miass, Russia.

Kaliochalcite, KCu2(SO4)2[(OH)(H2O)], a new tsumcorite-group mineral from the Tolbachik volcano, Kamchatka, Russia

The new tsumcorite-group mineral kaliochalcite, KCu 2 (SO 4 ) 2 [(OH)(H 2 O)] (IMA 2013–037), is found in several fumaroles at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Two fumaroles, Yadovitaya and Arsenatnaya, are considered as its type localities. The mineral seems to be a product of the interactions involving the high-temperature, sublimate KCu-sulphates and atmospheric water vapour at temperatures not higher than 100–150°C. Kaliochalcite mostly occurs in polymineralic crusts (up to several dozens cm 2 in area and up to 0.5 cm thick), where it is typically the major component. The mineral forms fine-grained pseudomorphs after anhydrous KCu-sulphates, mainly euchlorine, fedotovite or piypite, usually with their relics. Other associated minerals are hematite, tenorite, langbeinite, aphthitalite, steklite, lammerite, chlorothionite, gypsum, etc . Pseudo-rhombohedral or more complicated crystals of kaliochalcite (commonly up to 0.02 × 0.04 mm, rarely up to 0.03 × 0.1 mm) are observed in cavities. The mineral is light green, bright grass-green or almost colourless. Kaliochalcite is transparent in individuals and translucent in aggregates, with vitreous lustre. It is brittle, the Mohs’ hardness is 4. No cleavage was observed, the fracture is uneven. The caculated density, D calc , is 3.49 g cm −3 . Kaliochalcite is optically biaxial (+), α 1.630(3), β 1.650(3), γ 1.714(3), 2 V meas 55(10)°. The IR spectrum is given. The chemical composition (wt%, electron-microprobe data, H 2 O by selective sorption from the gaseous products of heating) is: Na 2 O 0.04, K 2 O 11.01, CaO 0.27, FeO 0.15, CuO 40.28, ZnO 0.39, SO 3 40.97, H 2 O 5.84, total 98.95. The empirical formula, calculated on the basis of 10 O apfu , is: (K 0.94 Ca 0.02 Na 0.01 ) Σ0.97 (Cu 2.03 Zn 0.02 Fe 0.01 ) Σ2.06 S 2.05 O 8.20 (OH) 1.01 (H 2 O) 0.79 . Kaliochalcite is monoclinic, space group C 2/ m, a 8.935(2), b 6.252(2), c 7.602(2) A, β 117.318(5)°, V 377.3(2) A 3 and Z = 2. The strongest reflections of the X-ray powder pattern [ d ,A( I )( hkl )] are: 6.78(100)(001), 3.484(70)(20–2), 3.249(63)(11–2), 2.892(77)(201), 2.852(83)(02–l), 2.554(72)(31–2, 22–1), 2.326(44)(22–2) and 1.693(37)(42–3, 22–4). The crystal structure was solved from single-crystal X-ray diffraction data, R = 0.100. The structure is built up from chains of edge-sharing Cu 2+ O 6 Jahn-Teller distorted octahedra connected by SO 4 tetrahedra and H-bonds to form {Cu 2 (SO 4 ) 2 [(OH)(H 2 O]} − layers. The linkage between these layers is provided by K + cations and H-bonds. Kaliochalcite is named as the potassium analogue of natrochalcite.

Whitecapsite, a new hydrous iron and trivalent antimony arsenate mineral from the White Caps mine, Nevada, USA

The new mineral species whitecapsite, H 16 Fe 2+ 5 Fe 3+ 14 Sb 3+ 6 (AsO 4 ) 18 O 16 ·120H 2 O, was found in the oxidation zone of the White Caps gold deposit (White Caps mine), Manhattan district, Nye Co., Nevada, USA, and named after the holotype locality. The mineral was found in cavities in a breccia consisting of fragments of jasperoid, silicified marble and mica schist, in association with picropharmacolite, guerinite, pitticite, gypsum, jarosite, goethite, sulfur, metastibnite and earlier quartz, calcite, kaolinite, realgar, stibnite, arsenopyrite, pyrite, sphalerite, orpiment, cinnabar and metacinnabar. Whitecapsite occurs as well-shaped hexagonal prismatic crystals (up to 0.3 × 0.3 × 1.5 mm) terminated with bipyramidal faces (forms: {110} and {111}) and as clusters of crystal up to 1 mm in maximal dimension. It is bright orange to golden-brownish orange, transparent, with a vitreous lustre. Mohs’ hardness is 2–2½. The mineral is brittle, cleavage was not observed, fracture is uneven. D meas = 2.30(3), D calc = 2.297 g cm −3 . Whitecapsite is optically uniaxial (+), ω = 1.590(2) and ɛ = 1.603(3). Chemical composition (wt%, electron probe) is: MnO 0.09, FeO 5.32, Fe 2 O 3 16.82, Sb 2 O 3 13.30, As 2 O 5 30.78, H 2 O calc 34.53, total 100.84. The empirical formula calculated on the basis of 208 O apfu with 256 H apfu is: H 16 Mn 2+ 0.08 Fe 2+ 4.95 Fe 3+ 14.07 Sb 3+ 6.10 As 5+ 17.89 O 88 ·120H 2 O. Both the IR and Raman spectra show high content of H 2 O, the presence of hydrated protons (the complex cations H + · n H 2 O) and an absence of OH groups. Sb L 3 and Fe K XANES spectra show the presence of only Sb 3+ and of both Fe 3+ and Fe 2+ (Fe 3+ > Fe 2+ ). Whitecapsite is hexagonal, P 6 3 / m , a = 16.0916(8), c = 21.7127(9) A, V = 4869.0(4) A 3 and Z = 1. The strongest reflections of the X-ray powder-diffraction pattern [ d ,A ( I ,%) ( hkl )] are: 13.99 (49) (100); 11.73 (100) (101); 5.267 (6) (120); 3.644 (4) (205, 132, 006); 2.999 (8) (411, 126, 225); 2.757 (4) (501, 234); 2.648 (5) (331, 414, 316). The crystal structure was solved by direct methods and refined to R = 0.058. Its major building unit is a heteropolyhedral cluster [(□,Fe 2+ ) 6 Fe 3+ 7 Sb 3 O 8 (AsO 4 ) 9 (H 2 O) 30 ] with the Fe 3+ O 6 trigonal prism as a central polyhedron. These clusters are isolated from each other and linked only via hydrogen bonds to the H 2 O molecules located in the interstitial space.

Chrysothallite K6Cu6Tl3+Cl17(OH)4·H2O, a new mineral species from the Tolbachik volcano, Kamchatka, Russia

Abstract 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 150 °C. It is associated with belloite, avdoninite, chlorothionite, sanguite, eriochalcite, mitscherlichite, sylvite, camallite and kainite at Glavnaya Tenoritovaya and with belloite, avdoninite, chlorothionite, eriochalcite, atacamite, halite, krohnkite, 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), ε = 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)∑6.10Tl0.97Cl17[(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)2 octahedra. Two Tl3+ cations occupy the centre of isolated TlCl6 and TlCl4(H2O)2 octahedra connected to each other and to the Cu polyhedral layers via KCl6 and KCl9 polyhedra. The name reflects the bright golden-yellow colour of the mineral (from the Greek χρυσός, gold) and the presence of thallium. Chrysothallite is the second known mineral with species-defining trivalent thallium.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. VI. Melanarsite, K3Cu7Fe3+O4(AsO4)4

Abstract The newmineralmelanarsite,K3Cu7Fe3+O4(AsO4)4,was found in the sublimates of theArsenatnaya 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(Cu7.02Fe3+0.95Al0.08Zn0.04Ti0.02)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) Å3 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)(1̄11), 6.084(17) (111), 4.595(26)(1̄31, 220, 2̄21), 3.124(22)(3̄31,1̄51), 2.763(20)(400, 1̄52), 2.570(23)(043) and 2.473(16) (260, 2̄61, 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 distortedCu(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).

Towards a revisitation of vesuvianite-group nomenclature: the crystal structure of Ti-rich vesuvianite from Alchuri, Shigar Valley, Pakistan.

Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, 27Al NMR, 57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å, space group P4/nnc. The structure was refined to final R1 = 0.031, wR2 = 0.057 for 11247 I > 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z = 2): [8-9](Ca17.1Na0.9) [8]Ca1.0[5](Fe2+0.44Fe3+0.34Mg0.22) [6](Al3.59Mg0.41) [6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral site Y2 is Al-dominant and does not contain transition elements. Another octahedral site Y3 is also Al-dominant and contains Fe2+, Fe3+ and Ti. The site Y1 is split into Y1a and Y1b predominantly occupied by Fe2+ and Fe3+, respectively. The role of the Y1 site in the diversity of vesuvianite-group minerals is discussed.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. VII. Pharmazincite, KZnAsO4

Abstract 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.

Nickeltsumcorite, Pb(Ni,Fe3+)2(AsO4)2(H2O,OH)2, a new tsumcorite-group mineral from Lavrion, Greece

Abstract A new tsumcorite-group mineral, nickeltsumcorite, Pb(Ni,Fe3+)2(AsO4)2(H2O,OH)2, the Ni-dominant analogue of tsumcorite and cobalttsumcorite, was found in the oxidation zone of a hydrothermal orebody containing gersdorffite and galena at the Km-3 mine, Lavrion, Attikí Prefecture, Greece. It is associated with annabergite, nickellotharmeyerite, nickelaustinite, gaspéite, calcite, dolomite, aragonite, quartz, goethite, cerussite, arseniosiderite, mimetite, oxyplumboroméite and Mn oxides/hydroxides. Nickeltsumcorite occurs as open-work aggregates and interrupted crusts up to 3 mm × 5 mm in area and up to 0.2 mm thick. They typically consist of coarse radial spherulites or dense concentric nodules up to 0.15 mm in diameter. Bunches or hemispherical clusters of crude individuals and separate imperfect, elongated crystals (up to 0.02 mm long) are also observed. Nickeltsumcorite is yellow, brownish-yellow, light brown or brown, with a yellow streak and a vitreous lustre. The Mohs hardness is ~4. The mineral is brittle; one direction of distinct cleavage is observed under the microscope. D(calc.) = 5.02 g cm-3. Nickeltsumcorite is optically biaxial (-), α = 1.82(2), β = 1.87(1), γ = 1.90(1), 2V(obs.) is large. The chemical composition (wt.%, electron-microprobe data, H2O by difference) is CaO 2.79, PbO 28.12, MgO 0.30, CoO 0.15, NiO 17.39, ZnO 0.76, Mn2O3 0.57, Fe2O3 6.83, As2O5 38.17, H2O 4.92, total 100.00. The empirical formula, calculated based on 10 O apfu, is (Pb0.76Ca0.30)Σ1.06(Ni1.39Fe3+0.51Zn0.06Mn3+0.04 Mg0.04Co0.01)Σ2.05As1.99O7.97[(H2O)1.25(OH)0.78]. The strongest reflections in the powder X-ray diffraction pattern [d,Å(I )(hkl)] are 4.64(100)(1̅11), 4.47(41)(2̅01), 3.238(82)(1̅12), 3.008(60)(201), 2.859(41)(021), 2.545(79)(3̅12, 112), 2.545(79)(3̅12, 112) and 2.505(61)(220, 2̅03). The cation composition, powder Xray diffraction data and IR spectrum show that nickeltsumcorite belongs to the tsumcorite structure type. The newmineral ismonoclinic, space group C2/m, a = 9.124(8), b = 6.339(3), c = 7.567(7) Å, β = 115.19(6)°, V = 396.0(7) Å3 and Z = 2. Nickeltsumcorite forms a solid-solution series with nickellotharmeyerite.