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The new zeolite-like titanosilicate mineral kamenevite K2TiSi3O9·H2O, isostructural with umbite K2ZrSi3O9·H2O, is found in two peralkaline pegmatites located at Mt. Suoluaiv (Oleniy Ruchey mine: holotype) and Mt. Rasvumchorr (Rasvumchorr mine) in the Khibiny alkaline complex, Kola peninsula, Russia. It is a hydrothermal mineral associated with lomonosovite, aegirine, villiaumite, pectolite, shafranovskite, ershovite, umbite, potassic feldspar, sodalite, lamprophyllite, etc. Kamenevite occurs as lamellar crystals up to 0.02 × 0.1 × 0.3 mm and their aggregates up to 0.7 mm (Oleniy Ruchey) or grains up to 0.15 mm across (Rasvumchorr). The mineral is transparent, colourless (white in aggregates), with vitreous lustre. It is brittle, the Mohs hardness is ca. 4. Cleavage is (010) good. D meas = 2.69(2), D calc = 2.698 g cm-3. Kamenevite is optically biaxial (–), a = 1.650(4), ß = 1.678(5), ? = 1.685(5), 2V meas = 60(10)°. The chemical composition of the holotype [wt%, electron microprobe data, H2O content calculated for 1 (H2O) pfu] is: Na2O = 0.48, K2O = 24.37, CaO = 0.13, Fe2O3 = 0.35, SiO2 = 48.78, TiO2 = 20.30, ZrO2 = 0.89, Nb2O5 = 0.35, H2O = 4.85, total = 100.50. The empirical formula calculated on the basis of 10 O atoms per formula unit (apfu) is (K1.92Na0.06Ca0.01)S1.99(Ti0.94Zr0.03Fe0.02Nb0.01)S1.00S3.01O9·H2O. Kamenevite is orthorhombic, P212121, a = 9.9166(4), b = 12.9561(5), c = 7.1374(3) Å, V = 917.02(6) Å3 and Z = 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 7.92(70)(110), 6.51(47)(020), 5.823(95)(101), 2.988(84)(301, 122), 2.954(100)(041, 320), 2.906(68)(311, 202) and 2.834(69)(141, 212). The crystal structure (single-crystal XRD data, R = 0.0384) is based on a microporous heteropolyhedral framework built by [Si3O9]8 wollastonite-type chains linked by isolated Ti-centred octahedra. The K+ cations and H2O molecules are located in wide and narrower [001] channels. The mineral is named in honour of the outstanding Russian geologist Evgeniy Arsenievich Kamenev (1934–2017) who made great contribution to the geology of the Khibiny complex.

The new mineral alexkhomyakovite K6(Ca2Na)(CO3)5Cl·6H2O (IMA2015-013) occurs in a peralkaline pegmatite at Mt. Koashva, Khibiny alkaline complex, Kola peninsula, Russia. It is a hydrothermal mineral associated with villiaumite, natrite, potassic feldspar, pectolite, sodalite, biotite, lamprophyllite, titanite, fluorapatite, wadeite, burbankite, rasvumite, djerfisherite, molybdenite and an incompletely characterized Na–Ca silicate. Alexkhomyakovite occurs as equant grains up to 0.2 mm, veinlets up to 3 cm long and up to 1 mm thick and fine-grained aggregates replacing delhayelite. Alexkhomyakovite is transparent to translucent, colourless, white or grey, with vitreous to greasy lustre. It is brittle, the Mohs hardness is ca. 3. No cleavage was observed, the fracture is uneven. D meas = 2.25(1), D calc = 2.196 g cm-3. Alexkhomyakovite is optically uniaxial (–), ? = 1.543(2), e = 1.476(2). The infrared spectrum is reported. The chemical composition [wt%, electron microprobe data, CO2 and H2O contents calculated for 5 (CO3) and 6 (H2O) per formula unit (pfu), respectively] is: Na2O 4.09, K2O 35.72, CaO 14.92, MnO 0.01, FeO 0.02, SO3 0.11, Cl 4.32, CO2 28.28, H2O 13.90, –O=Cl –0.98, total 100.39. The empirical formula calculated on the basis of 9 metal cations pfu is K5.90Ca2.07Na1.03(CO3)5(SO4)0.01O0.05Cl0.95·6H2O. The numbers of CO3 groups and H2O molecules are based on structure data. Alexkhomyakovite is hexagonal, P63/mcm, a = 9.2691(2), c = 15.8419(4) Å, V = 1178.72(5) Å3 and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d Å(I)(hkl)] are: 7.96(27)(002), 3.486(35)(113), 3.011(100)(114), 2.977(32)(211), 2.676(36)(300), 2.626(42)(213, 115), 2.206(26)(311) and 1.982(17)(008). The crystal structure (solved from single-crystal X-ray diffraction data, R = 0.0578) is unique. It is based on (001) heteropolyhedral layers of pentagonal bipyramids (Ca,Na)O5(H2O)2 interconnected via carbonate groups of two types, edge-sharing ones and vertex-sharing ones. Ca and Na are disordered. Ten-fold coordinated K cations centre KO6Cl(H2O)3 polyhedra on either side of the heteropolyhedral layer. A third type of carbonate group and Cl occupy the interlayer. The mineral is named in honour of the outstanding Russian mineralogist Alexander Petrovich Khomyakov (1933–2012).

The crystal structures of two Cr-rich pumpellyite-group minerals, shuiskite with 22.6 wt% Cr2O3 from the Biserskoe deposit and chromian pumpellyite-(Mg) with 16.4 wt% Cr2O3 from the Glavnoe Saranovskoe deposit (both belong to the Saranovskaya group of chromite deposits, Middle Urals, Russia) were studied through single-crystal X-ray diffraction. The structures (space group C2/m) of shuiskite with a = 19.2156(7), b = 5.9779(2), c = 8.8268(3) A°, ß = 97.785(3)° and chromian pumpellyite-(Mg) with a = 19.1776(8), b = 5.9537(3), c = 8.8282(4) A°, ß = 97.668(4)° were refined to R 1 = 3.01 and 3.12%, respectively; the structure of shuiskite was determined for the first time. The formulae (Z = 4) obtained from the structural refinements and taking into account electron-microprobe data are: W Ca2.00 X (Mg0.46Cr0.36Al0.18)S1.00 Y (Cr1.04Al0.96)S2.00 Z Si3.00O10.54OH3.46 for shuiskite and W Ca2.00 X (Mg0.50Cr0.30Al0.20)S1.00 Y (Al1.30Cr0.70)S2.00 Z Si3.00O10.50OH3.50 for chromian pumpellyite-(Mg). Molecular water is absent in both minerals. The presence of silanol groups Si–OH is confirmed by Infrared (IR) spectroscopy. The existence of shuiskite as an individual mineral in its initial sense, i.e., with Mg and Cr3+ dominant at the X and Y sites, respectively, is confirmed. The simplified formula of shuiskite has been refined: Ca2(Mg,Cr)(Cr,Al)2[SiO4][Si2O6(OH,O)](OH,O)(OH)2. The simplified formula of chromian pumpellyite-(Mg) is Ca2(Mg,Cr)(Al,Cr)2[SiO4][Si2O6(OH,O)](OH,O)(OH)2. In high-chromium pumpellyite-group minerals the preference of Cr for the Y site increases with increasing total Cr content: the distribution coefficient of Cr3+ between the X and Y sites, K D = (Cr/Al) X /(Cr/Al) Y , is 2.79 in chromian pumpellyite-(Mg) and 1.85 in shuiskite.

The crystal structures of four betalomonosovite samples from peralkaline pegmatites of the Khibiny alkaline complex, Kola Peninsula, Russia, were studied using single-crystal X-ray diffraction. The samples represent different chemical and structural varieties of betalomonosovite. The suggested general formula of betalomonosovite, based on the empirical data known to date, is Na5?+?x Ti4[Si2O7]2[PO3(OH)]2?-?y [PO2(OH)2] y O2[(OH,F)2?-?z O z ], where 0?=?x?=?2, 0?=?y?=?1 and 0?=?z?=?1. Betalomonosovite is a transformation product of lomonosovite, Na10Ti4(Si2O7)2(PO4)2O4, due to the leaching of Na and protonation of O atoms of phosphate groups and Ti–O–Ti bridges. Distinctive features of betalomonosovite are: (a) the presence of H+ in the form of species-defining acid phosphate anion(s) [PO2(OH)2]?±?[PO3(OH)]; (b) the presence of OH- anion at the Ti–O–Ti bridges in the O sheet of the HOH block and c) deficiency of Na (as compared to lomonosovite) in an amount related to the degree of protonation. A hypothetical end-member product of lomonosovite alteration with the simplified formula Na4Ti4[Si2O7]2[PO2(OH)2]2O2(OH)2 has not been reported in Nature yet. The ways and the degree of alteration may vary significantly, resulting in significant variations in both crystal structure and chemical composition, including the Na content, the degree of the substitution of O by OH, unit-cell dimensions and splitting of the P, O and/or Na sites.

The new mineral genplesite, Ca3Sn(SO4)2(OH)6·3H2O, the first natural tin sulfate, is found in cavities in massive chalcopyrite ore at the Oktyabr'skoe Cu-Ni-Pd-Pt deposit (Oktyabr'sky mine), Talnakh, Norilsk district, Siberia, Russia. It is a late-stage hydrothermal mineral associated with greenalite, chamosite, pectolite, ferroactinolite, calcite and fluorapatite. Genplesite occurs as equant, short prismatic or thick tabular hexagonal crystals up to 0.5?mm and crystal clusters up to 0.6?×?1.2?mm. The major crystal forms are {1?0?0} and {0?0?1} whereas {1?0?2} and {1?0?1} are minor. Genplesite is transparent, colourless, with vitreous lustre. It is brittle, the Mohs hardness is ca. 3. Cleavage is not observed, the fracture is conchoidal. D meas?=?2.78(1), D calc?=?2.773?g?·?cm-3. Genplesite is optically uniaxial (–), ??=?1.597(2), e?=?1.572(2). The IR spectrum is reported. The chemical composition (wt%, electron microprobe data, H2O calculated for 3 molecules per formula unit, pfu) is: CaO 28.67, Al2O3 0.11, GeO2 0.50, SnO2 24.20, SO3 27.25, H2Ocalc 18.34, total 99.07. The empirical formula calculated on the basis of 17 O apfu is: Ca3.01(Sn0.95Ge0.03Al0.01)S0.99S2.01O8(OH)6·3H2O. Genplesite is hexagonal, P63/mmc, a?=?8.5139(2), ??=?11.1408(3)?Å, V?=?699.37(1)?Å3 and Z?=?2. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 7.38(68)(1?0?0), 4.259(46)(1?1?0), 3.503(15)(2?0?1), 3.383(1?0?0)(1?1?2), 2.616(13)(2?0?3), 2.493(14)(2?1?2), 2.249(14)(3?0?2) and 2.130(17)(1?0?5, 2?2?0). Genplesite is a member of the fleischerite group. Its crystal structure was solved from single-crystal X-ray diffraction data (R?=?0.016). The major building unit of the structure is a column consisting of isolated Sn4+(OH)6 octahedra and trimers of edge-sharing CaO2(OH)4(H2O)2 polyhedra. Adjacent columns are interconnected via H2O molecules and SO4 tetrahedra. Genplesite is named in honour of Gennadiy N. Plesin (b. 1963), a mine surveyor at the Oktyabr'sky mine and an amateur mineralogist who found the mineral.

This paper is a review devoted to a special type of arsenic mineralization related to volcanic fumaroles of the oxidizing type. Fifty-four hydrogen-free arsenates (40 valid species and 14 insufficiently characterized phases) with Cu2+, Mg, Al, Fe3+, Ti4+, Zn, Ca, Na, and K are identified here and 46 of them are endemics of fumarolic formation. Fifty-three of them have been found in active fumaroles at the Tolbachik volcano, Kamchatka, Russia. Thirty different structure types have been established for fumarolic arsenates, including 19 previously unknown among minerals. The alkali-richest (>17?wt% Na2O?+?K2O) and Ti-richest (12–28?wt% TiO2) natural arsenates occur in Tolbachik fumaroles. Nineteen fumarolic arsenates with Cu2+, Al, Fe3+ or Ti contain additional O2- anions. The major fumarolic arsenates at Tolbachik are alluaudite-group members (johillerite, calciojohillerite, nickenichite, bradaczekite and badalovite), lammerite, svabite, tilasite, berzeliite and urusovite. All Tolbachik arsenates crystallized at temperatures =450?°C (the major assumed temperature interval is 500–750?°C), under atmospheric pressure and high oxygen fugacity. They were precipitated directly from the gas phase as volcanic sublimates, or were formed as a result of gas–rock interaction in fumarolic cameras, where the host basalt was the source of the less volatile elements Al, Ti, Mg and Ca. The empirical data on fumarolic As5+ minerals are summarized and discussed, including their chemistry, crystal chemistry (with special attention paid to isomorphic substitutions and solid solutions) and occurrence. Electron-microprobe analyses illustrating the chemical diversity and variability of 53 fumarolic arsenates are given as supplementary data, as well as a photographic documentation of their morphology and paragenetic relationships.

A new mineral feodosiyite Cu11Mg2Cl18 (OH)8·16H2O is found in the Glavnaya Tenoritovaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Closely associated minerals are belloite, avdoninite, sylvite, carnallite, chlorothionite, and dioskouriite. Feodosiyite forms tabular or prismatic crystals up to 0.02×0.1×0. 1mm3 combined in interrupted incrustations up to 0.1×0.5×1cm3 overgrowing basalt scoria. The mineral is transparent, bright green, with vitreous lustre. Feodosiyite is brittle. Its Mohs’hardness is ca 3. One direction of imperfect cleavage was observed, the fracture is uneven. Dmeas = 2.57 (1), Dcalc = 2.563 g cm–3. Feodosiyite is optically biaxial (–), a =1.660 (3), ß =1.690 (5), ? =1. 718 (5), 2Vmeas = 90 (5)°. The Raman spectrum is reported. The chemical composition (wt. %, electron-microprobe data, H2O calculated by total difference) is: MgO 5.39 (4.84–5.91), Cu 46.98, Cl 35.42, H2Ocalc 20.21, –O = Cl –8.00, total 100.00. The empirical formula calculated based on 42 atoms O+Cl pfu is: Cu10.58Mg2.40Cl17.90 (OH)8.06·16.04H2O. Feodosiyite is monoclinic, P21/c, a =12.9010 (6), b =16.4193 (5), c =11.9614 (5) Å, ß =113.691 (6)º, V = 2320.20 (17) Å3 and Z = 2. The strongest reflections of the powder XRD pattern [d, Å (I) (hkl)] are: 11.87 (100) (100), 6.585 (15) (021), 5.969 (25) (–102), 5.905 (16) (200), 5.231 (13) (121), 3.135 (8) (222, –412, –151) and 2.924 (11) (–333, –251). The crystal structure, solved from single-crystal XRD data [R1 (F) = 0.0867], is unique. It is based on layers of Cu2+-centred polyhedra. Cu2+ cations occupy six crystallographically non-equivalent sites that are placed in distorted octahedra Cu (1, 3, 5) (OH)2Cl4, Cu (2) (OH)3Cl3, and Cu (6) (OH)2 (H2O)Cl3 and distorted tetragonal pyramids Cu (4) (OH)2Cl3. Isolated almost regular Mg (H2O)6 octahedra, linked with the layers of Cu-centred polyhedra by H-bonds, occur in the interlayer space, as well as separate H2O molecules. The mineral is named in honour of the outstanding Russian geologist Feodosiy Nikolaevich Chernyshev (1856–1914).

The new mineral calciomurmanite, (Na,[])2 Ca(Ti, Mg, Nb)4 [Si2 O7]2 O2 (OH, O)2 (H2 O)4, a Na-Ca ordered analogue of murmanite, was found in three localities at Kola Peninsula, Russia: at Mt. Flora in the Lovozero alkaline complex (the holotype) and at Mts. Eveslogchorr (the cotype) and Koashva, both in the Khibiny alkaline complex. Calciomurmanite is a hydrothermal mineral formed as a result of late-stage, low-temperature alteration (hydration combined with natural cation exchange) of a high-temperature, anhydrous phosphate-bearing titanosilicate, most likely lomonosovite and/or betalomonosovite, in the peralkaline (hyperagpaitic) rocks. The holotype sample is associated with microcline, aegirine, lorenzenite and fluorapatite, whereas the cotype sample occurs with microcline, aegirine, lamprophyllite, tsepinite-Ca and tsepinite-K. The mineral occurs as lamellae up to 0.1 × 0.4 × 0.6 cm, sometimes combined in fan-shaped aggregates up to 3.5 cm. Calciomurmanite is pale brownish or purple; the streak is white. The lustre is nacreous on cleavage surface and greasy on broken surface across cleavage. The (001) cleavage is perfect, mica-like; the fracture is stepped. Dmeas = 2.70(3), Dcalc = 2.85 g cm–3. The mineral is optically biaxial (–), a = 1.680(4), ß = 1.728(4), ? = 1.743(4), 2 V meas = 58(5)º. The IR spectrum is reported. The chemical composition (wt%, electron-microprobe data, H2 O by the Alimarin method) is: Na2 O 5.39, K2 O 0.30, CaO 7.61, MgO 2.54, MnO 2.65, FeO 1.93, Al2 O3 0.85, SiO2 30.27, TiO2 29.69, Nb2 O5 6.14, P2 O5 0.27, H2 O 11.59, total 99.23. The empirical formula of the holotype sample, calculated on the basis of Si + Al = 4 apfu, is: Na1.34 Ca1.04 K0.05 Mg0.49 Mn0.29 Fe0.21 Nb0.36 Ti2.85 (Si3.87 Al0.13)S4 O16.40 (OH)1.60 (PO4)0.03 (H2 O)4.94. Calciomurmanite is triclinic, P -1, a = 5.3470(6), b = 7.0774(7), c = 12.146(1) Å, a = 91.827(4), ß = 107.527(4), ? = 90.155(4)º, V = 438.03(8) Å3 and Z = 1. The strongest reflections of the X-ray powder pattern [d, Å(I)(hkl)] are: 11.69(100)(001), 5.87(68)(011, 002), 4.25(89) (-1-11, -111), 3.825(44)(-1-12, 003, -112), 2.940(100)(-1-21, -121), 2.900(79)(004, 120). The crystal structure was solved by direct methods from single-crystal low-temperature (200 K) X-ray diffraction data and refined to R = 0.0656 for the holotype and 0.0663 for the cotype. The structure is based on a three-sheet HOH block: an octahedral (O) sheet containing alternating chains of NaO6 and TiO6 octahedra and two heteropolyhedral (H) sheets consisting of Si2 O7 groups, TiO6 octahedra and CaO8 polyhedra. H2 O molecules occupy two sites in the interlayer space.

Raisaite, CuMg[Te6+ O4 (OH)2] ·6H2 O, is a new mineral found at the Sentyabr'skoe deposit, Ilirney ore district, Western Chukotka, North-Eastern Region, Russia. It is associated with gypsum, malachite, azurite, cerussite, anglesite, brochantite, linarite, posnjakite, chlorargyrite, acanthite, gold, brucite, goethite, coronadite, paratellurite, and xocomecatlite in the oxidation zone of quartz veins with calcite, dolomite, ankerite, muscovite, pyrite, chalcopyrite, galena, sphalerite, hessite, petzite, altaite, primary acanthite and gold, etc. Raisaite occurs as prismatic crystals (up to 0.1 x 0.6 mm), as groups or crusts (up to 0.4 x 0.6 mm) and as dense roundish clusters (up to 0.2 mm in diameter) forming botryoidal aggregates (up to 1 mm across). Raisaite is transparent, light blue to bright sky blue, with a vitreous lustre. Its Mohs' hardness is ca. 2. Cleavage is imperfect, probably on (100), the fracture is uneven. D meas = 2.82(1), D calc = 2.828 g cm3. Raisaite is optically biaxial (+), a = 1.626(3), ß = 1.642(5), ? = 1.665(3) and 2 V meas = 80(10)° . The IR spectrum is reported. The chemical composition (average of 7 analyses, H2 O by difference) is: MgO 10.68, CuO 18.09, SO3 0.44, TeO3 41.19, H2 Ocalc 29.60, total 100.00 wt%. The empirical formula calculated on the basis of 12 O apfu is: Cu0.96 Mg1.11 Te0.99 S0.02 O4.20 (OH)1.80 6.00H2 O. Raisaite is monoclinic, C 2/ c , a = 9.9078(2), b = 10.1325(3), c = 9.8375(2) Å, ß = 91.839(2)Å, V = 987.09(4)Å 3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 7.088(100)(110), 5.815(35)(–111), 5.690(23)(111), 4.949(91)(200, 002), 4.507(50)(021), 3.533(17)(–202, 022), 3.358(17)(–221), 3.310(21)(221) and 2.694(29)(–132). The crystal structure (solved from single-crystal X-ray diffraction data, R = 0.0186) is unique. It is based on heteropolyhedral zig-zag chains built by alternating edge-sharing Te6+O4 (OH)2 and CuO4 (H2 O)2 octahedra. Mg(H2 O)6 octahedra are connected with the chains from two sides via common O vertices. Adjacent chains are bound by H-bonding forming ''layers'' which are connected with each other by a system of H-bonds. The mineral is named in honour of the Russian mineralogist Raisa A. Vinogradova (born 1935), Moscow State University. Both the new mineral and its name have been approved by the IMA CNMNC (IMA2014-046).

The new mineral zincomenite, ß-ZnSeO3, is found in active fumaroles belonging to the Northern fumarole field at the First scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with sofiite, sellaite, fluorite, halite, anhydrite, cotunnite, chubarovite, flinteite, etc. Zincomenite occurs as tabular, equant or prismatic crystals up to 0.2 mm sometimes combined in clusters up to 0.3 mm across, or interrupted incrustations up to 0.7 × 1 cm overgrowing basalt scoria. Partial to complete pseudomorphs of zincomenite after sofiite are typical. The crystal forms are {101}, {010}, {100} and {013}. T-shaped twins with (012) as twin plane were found. Zincomenite is transparent, colourless, white or pale beige with adamantine lustre. Cleavage and parting were not observed and the fracture is uneven. D calc is 4.760 g cm-3. Zincomenite is optically biaxial (-), a = 1.744(5), ß = 1.860(5), ? = 1.875(5). The IR spectrum is reported. The chemical composition (wt.%, electron microprobe data) is: ZnO 42.53, SeO2 56.67, total 99.20. The empirical formula calculated on the basis of 3 O apfu is: Zn1.02Se0.99O3. Zincomenite is orthorombic, Pbca, a = 7.1971(2), b = 6.2320(2), c = 11.9914(3) Å, V = 537.84(2) Å3 and Z = 8. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.612(26)(102), 3.601(77)(200), 3.119(48)(210), 3.048(38)(113), 3.014(100)(211, 021), 2.996(56)(004), 2.771(19)(123, 104, 212), 2.459(23)(213, 023), 2.311(20)(123, 221, 204), and 2.162(19)(214, 024). Zincomenite is a representative of the CuSeO3 structure type. Its crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0188), contains layers formed by Zn2O8 dimers (consisting of edge-sharing ZnO5 trigonal bipyramids; each dimer shares four vertices with the neighbouring ones) linked via (SeO3)2- groups (with Se4+ in trigonal pyramidal coordination) to form an open framework. The mineral is named in allusion to its chemical composition: zinc selenite (the Greek µ??a? means moon, indicating selenium).

The crystal structure of a new natural compound NaCu2Cl3[N3C2H2]2[NH3]2·4H2O, (further denoted Iin the text) from a guano deposit located on the Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile, was studied by single-crystal low-temperature (200 K) XRD, R=2.42%. The compound Iis orthorhombic, space group P212121; a=19.484(3), b=7.2136(10), c=11.999(4) Å, V=1686.5(7) Å3, Z=4. The crystal structure of Icontains zig-zag chains of the corner-sharing Cu(1)-centered octahedra running along the aaxis and isolated Cu(2)-centered octahedra connected with the chains via1,2,4-triazolate anions. This structural fragment is close to that found in the mineral chanabayaite, Cu2(N3C2H2)2Cl(NH3, Cl, H2O, □)4. In contrast to Na-free chanabayaite, in the structure of INa cations occupy Na(H2O)6octahedra connected viacommon edges to form chains parallel to the chains of Cu(1)-centered octahedra. Iis the second natural compound, after chanabayaite, with 1,2,4-triazolate anions N3C2H2–and is assumed to be a protophase of chanabayaite; the latter was presumably formed as a result of Na and Cl leaching and dehydration of I.

The new mineral cryobostryxite, KZnCl3 · 2H2O, is found in the Northern fumarole field at the First scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Cryobostryxite is a secondary mineral formed in the upper, moderately hot (30–80°C) zone of active fumaroles, probably as a product of the interactions between high-temperature volcanic sublimates and meteoric water. It is associated with gypsum, ralstonite and opal; earlier, primary minerals of the assemblage are sellaite, fluorite, halite, anhydrite, cotunnite, sofiite, flinteite, chubarovite, anglesite, challacolloite, zincomenite, saltonseaite, hollandite, hematite, jakobssonite, leonardsenite and olsacherite. Cryobostryxite occurs as anthodites (up to 0.5 x 2 mm), their aggregates (up to 4 x 5 mm), granular crusts (up to 2 x 2 mm) and, rarely, coarse prismatic to acicular crystals (up to 0.2 x 1 mm). The mineral is transparent, colourless, with vitreous lustre. It is brittle, cleavage is not observed. The Mohs hardness is ca. 2. D meas = 2.30(2), D calc = 2.300 g cm-3. Cryobostryxite is optically biaxial (+), a = 1.522(2), ß = 1.530(2), ? = 1.576(2) and 2 V meas = 30(15)°. The chemical composition (wt.%, electron-microprobe data, H2O calculated for 2 molecules per formula unit, pfu) is: K 14.85, Tl 4.08, Zn 25.82, Cl 41.70, H2O(calc.) 14.19, total 100.64. The empirical formula calculated on the basis of K + Tl + Zn + Cl = 5 apfu is (K0.96 Tl+ 0.05)s1.01Zn1.00Cl2.992H2O. Cryobostryxite is monoclinic, P21/c, a = 6.2795(3), b = 10.1397(3), c = 12.0829(7) Å , ß = 107.732(5)° , V = 732.79(6) Å 3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.62 (30) (011), 5.986 (43) (100), 5.766 (35) (002), 3.907 (33) (–121), 3.466 (20) (121), 3.062 (100) (–202, 023), 2.996 (24) (–211, 200) and 2.853 (27) (–114). The crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0654), contains isolated Zn-centred tetrahedra ZnCl3 (H2O) connected via eight-coordinated K-centred polyhedra KCl7 (H2O) to form a pseudo-framework. Both Zn- and K-centred polyhedra involve only O(1) atoms of the H2 O(1) molecules, whereas H2O(2) molecules are located in holes of the K-Zn-Cl-H2 O(1) polyhedral pseudo-framework. The mineral name is based on two Greek words, ?????, cold or ice, and ß?st???, curl, reflecting the typical appearance: visually, anthodites of the mineral are very similar to ice curls. A novel chemical family of minerals including the potassium zinc chlorides flinteite K2 ZnCl4, mellizinkalite K3 Zn2 Cl7 and cryobostryxite is discussed in the light of crystal-chemical data and formation conditions.

The crystal structure of vigrishinite, an epistolite-group heterophyllosilicate with essential Zn, has been reinvestigated; the ideal end-member formula is revised to Zn2Ti4-x (Si2O7)2O2(OH,F,O)2(H2O,OH,)4 with x<1. Structure models of Zn-exchanged forms of murmanite after 5 and 24 hour experiments with 1N ZnSO4 solution at 90 °C have been obtained from single-crystal X-ray diffraction data. The structural formulae are [B1]Ca0.04{Na1.22(Ti1.19Mn0.60Nb0.21)}{[A1,A2]Zn1.03(Ti1.64Nb0.36)[Si2O7]2}O2(O,OH)2(H2O)4 for vigrishinite and {Na1.14(Ti1.45Mn0.50Nb0.05)}{[A1]Ca0.77 [A2]Zn0.13(Ti1.85Nb0.15)[Si2O7]2}O2(OH,O)2(H2O)4 and [B1]Zn0.15 [B2]Ca0.18{Na1.06(Ti1.32Mn0.60Nb0.08)}{[A1]Zn0.70 [A2]Ca0.12(Ti1.74Nb0.26)[Si2O7]2}O2(OH,O)2(H2O)4 for the 5 and 24 hour Zn-exchanged forms of murmanite, respectively (braces give successively the contents of the octahedral O and heteropolyhedral H sheets). The triclinic (P–1) unit-cell parameters are respectively: a = 8.7127(17), 8.871(3), 8.748(2) Å; b = 8.6823(17), 8.844(6), 8.724(2) Å; c = 11.746(2), 11.734(6), 11.675(3) Å; a = 91.481(4), 92.75(3), 92.503(13)°; ß = 98.471(4), 97.60(4), 97.846(13)°; ? = 105.474(4), 106.23(2), 105.875(13)°; V = 845.0(3), 872.7(8), 845.9(4) Å3. Our data (1) confirm that vigrishinite was formed as a result of natural ion-exchange of murmanite Na4Ti4 (Si2O7)2O4 · 4H2O with Zn2+ in low-temperature solutions; (2) prove that direct transformation of lomonosovite Na4Ti4(Si2O7)2O4 · 2Na3PO4 into vigrishinite, without prior leaching of Na+ and PO4 3– from the former and formation of murmanite, is unlikely; (3) suggest the following ion-exchange mechanism: during the early stage Na+ leaches into the solution whereas Ca2+, a common admixture in murmanite, migrates into one of the sites in the H sheet, leaving another site vacant for further entry of Zn; in the next stage Zn2+ enters the emptied site in the H sheet and, in small amount, into the interlayer whereas Ca2+ partly moves from the H sheet into the interlayer; (4) show the transformation of the murmanite-type unit cell (P1; V ˜ 440 Å3) into the vigrishinite-type cell with a and b parameters corresponding to the ab face diagonals of the former during the first stage of the exchange with Zn, due to ordering in the H sheet. New findings of vigrishinite in two pegmatites of the Lovozero massif, Kola peninsula, Russia (at Severnyi open pit, Mt. Alluaiv and at Pegmatite #60, Mt. Karnasurt) in the same setting as at the type locality, i.e. only in close contact with cavities after dissolved sphalerite, show that the ion exchange in epistolite-group heterophyllosilicates is not uncommon in Nature. Our data indicate there is a continuous solid solution between murmanite and vigrishinite.

The new mineral kononovite, NaMg(SO4)F, the first sulphate member of the durangite (tilasite) group, 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 closely associated with langbeinite, hematite, anglesite and euchlorine. Uklonskovite is a product of the supergene alteration of kononovite. The new mineral occurs as prismatic to thick tabular crystals up to 0.04 × 0.06 × 0.1 mm, isolated or, more typically, forming clusters or interrupted crusts up to several cm2 in area and up to 0.05 mm thick overgrowing basalt scoria. Kononovite is white, transparent in tiny grains and translucent in blocky crystals, with vitreous lustre. It is brittle but with signs of weak plasticity; one direction of imperfect cleavage is observed. The Mohs' hardness is ca. 3. D meas = 2.91(1), D calc = 2.945 g cm3. Kononovite is optically biaxial (+), a = 1.488(2), ß = 1.491(2), ? = 1.496(2), 2V meas = 75(5)°. The IR spectrum is reported. The chemical composition (wt%, electron-microprobe data) is: Na2O 18.68, K2O 0.14, MgO 24.77, ZnO 0.28, PbO 0.10, SO3 48.44, F 11.82, Cl 0.12, O = (F,Cl) –5.00, total 99.35. The empirical formula calculated on the basis of 5 (O + F + Cl) anions pfu is: Na0.99K0.01Mg1.01Zn0.01S0.99O3.97F1.02Cl0.01. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.766(38)(–111), 3.567(33)(021), 3.233(82)(–112), 3.210(55)(002), 3.041(100)(200), 2.589(53)(130), 2.571(38)(022) and 2.269(33)(131). Kononovite is monoclinic, space group C2/c [by analogy with synthetic NaMg(SO4)F which is practically identical to the mineral in its powder XRD pattern], a = 6.662(2), b = 8.584(3), c = 7.035(2) Å, ß = 114.06(3)°, V = 367.4(1) Å3 and Z = 4. The mineral is named in honour of the Russian mineralogist Oleg V. Kononov (born 1932), Moscow State University. Two types of fluorine mineralization in deposits of the Tolbachik fumaroles are discussed.

The paper presents the first data on the crystal chemistry of the cation-exchanged forms of layered titanosilicates belonging to the epistolite group. It was found that these heterophyllosilicates have high exchange capacity and selectivity for cations of chalcophile elements (Ag, Cu and Zn) and could be considered as potentially novel raw materials or, more likely, as possible prototypes of cation-selective synthetic microporous materials. The crystal structures of Ag- and Cu-exchanged forms of lomonosovite and Ag-exchanged form of murmanite were studied by single-crystal X-ray diffraction. The topology of the main structural unit, the HOH block, remains unchanged in cation-exchanged forms as compared to the initial lomonosovite Na4Ti4 (Si2O7)2O4 · 2Na3PO4 (P-1) and murmanite Na4Ti4(Si2O7)2O4 · 4H2O (P-1). In Ag-exchanged murmanite, Ag cations occupy two crystallographically non-equivalent positions: one in the heteropolyhedral (H) sheet and another one in the octahedral (O) sheet corresponding to the positions of Na in initial murmanite. The crystal structure of the Ag-exchanged form of lomonosovite is characterized by an increased unit-cell parameter c and doubled parameter b as compared to initial lomonosovite. Ten large-cation sites statistically occupied by Ag and Na correspond to the Na sites in the initial lomonosovite: six in the interlayer space, two in the H sheet and two in the O sheet. Silver significantly replaces Na in sites in the interlayer space and in the O sheet, whereas sites in the H sheet are less affected by the ion exchange. Unit-cell parameter c of the Cu-exchanged form of lomonosovite decreases by 3.58 % as compared to the initial lomonosovite whereas a and b remain almost the same. The Cu cations occupy two crystallographically independent positions. The Cu(1) site, corresponding to the Na(3) site in the initial lomonosovite, is located in the interlayer space. The low-occupancy Cu(2) site is located on the inversion centre in the O sheet; this site is vacant in the initial lomonosovite. The Cu(2) site is surrounded by six O atoms forming an octahedron distorted due to the Jahn-Teller effect.

The new mineral mellizinkalite, K3Zn2Cl7, is found in the Glavnaya Tenoritovaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Associated minerals are belloite, avdoninite, eriochalcite, sylvite, halite, carnallite, mitscherlichite, sanguite, chrysothallite, romanorlovite, gypsum, chlorothionite, kainite and earlier hematite, tenorite and chalcocyanite. Mellizinkalite occurs as irregularly shaped grains up to 0.5 mm across or crude elongated crystals up to 0.25 × 1.3 mm, their clusters and crusts up to 2 × 2 mm in area and up to 0.5 mm thick. The mineral is yellow-brown to reddish brown, transparent, with vitreous lustre. It is moderately brittle, slightly plastic. The Mohs' hardness is ca. 2. Cleavage is not observed, the fracture is uneven. D meas = 2.46(2) and D calc = 2.49 g cm–3. Mellizinkalite is optically biaxial (–), a = 1.556(5), ß = 1.612(5), ? = 1.663(5) and 2V meas = 85(5)°. The Raman spectrum is reported. The chemical composition (wt.%, electron-microprobe data) is: K 23.5, Rb 0.52, Mg 0.47, Cu 1.77, Zn 24.4, Cl 50.0, total 100.7. The empirical formula calculated on the basis of 12 atoms pfu is: (K2.95Rb0.03)S 2.98(Zn1.84Cu0.14Mg0.09)S 2.07Cl6.95. Mellizinkalite is triclinic, P1, a = 6.7737(4), b = 10.5715(13), c = 11.0730(9) Å, a = 117.930(10), ß = 106.909(5), ? = 90.389(8)°, V = 660.61(10) Å3 and Z = 2. The strongest reflections of the X-ray powder pattern [d,Å (I) (hkl)] are: 9.20(69)(001, 010, 0–11), 6.40(100)(100), 5.712(47)(–110, 1–11), 4.608(92)(002, 020), 3.499(55)(012), 3.473(73)(0–13, 0–31, 0–23), 3.393(66)(–201) and 3.075(49)(003). The crystal structure, solved from single-crystal X-ray diffraction data (R = 0.065), is unique. It consists of alternating layers of different ZnCl4 polyhedra. The Zn(1) cations are located in flat squares which are connected to each other via common Cl-Cl edges to form Zn2Cl6 dimers, whereas Zn(2) cations occupy isolated tetrahedra. Potassium cations occupy sites between the layers of Zn-centred polyhedra. The mineral (IMA2014–010) is named from three Latin words, mellis – honey, zincum and kalium, alluding to its colour and species-defining cations, zinc and potassium.

The new mineral species whitecapsite, H16Fe2+ 5Fe3+ 14Sb3+ 6(AsO4)18O16·120H2O, 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 x 0.3 x 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. Dmeas = 2.30(3), Dcalc = 2.297 g cm–3. Whitecapsite is optically uniaxial (+), ? = 1.590(2) and e = 1.603(3). Chemical composition (wt%, electron probe) is: MnO 0.09, FeO 5.32, Fe2O3 16.82, Sb2O3 13.30, As2O5 30.78, H2Ocalc 34.53, total 100.84. The empirical formula calculated on the basis of 208 O apfu with 256 H apfu is: H16Mn2+ 0.08Fe2+ 4.95Fe3+ 14.07Sb3+ 6.10As5+ 17.89O88·120H2O. Both the IR and Raman spectra show high content of H2O, the presence of hydrated protons (the complex cations H+·nH2O) and an absence of OH groups. Sb L 3 and Fe K XANES spectra show the presence of only Sb3+ and of both Fe3+ and Fe2+ (Fe3+ > Fe2+). Whitecapsite is hexagonal, P63/m, a = 16.0916(8), c = 21.7127(9) Å, V = 4869.0(4) Å3 and Z = 1. The strongest reflections of the X-ray powder-diffraction pattern [d,Å (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 [(, Fe2+)6Fe3+ 7Sb3O8(AsO4)9(H2O)30] with the Fe3+O6 trigonal prism as a central polyhedron. These clusters are isolated from each other and linked only via hydrogen bonds to the H2O molecules located in the interstitial space.

The article features the Rubtsovskiy copper mine in western Siberia which contains the mineral cuprite. Topics include the crystallized specimens of native copper found in the Rubtsovskoe deposit during the late 2000s, previous studies and research conducted in the area which looked at the structure, mineralogy, and origins of the deposit, and a brief history of the mine which was discovered on June 27, 1970.