N. V. Zubkova

Cupromolybdite, Cu3O(MoO4)2, a new fumarolic mineral from the Tolbachik volcano, Kamchatka Peninsula, Russia

Cupromolybdite is a new fumarolic mineral from the New Tolbachik scoria cones of Tolbachik volcano, Kamchatka Peninsula, Russia. Cupromolybdite forms prismatic crystals up to 150 μm in length or acicular crystals with a thickness and length of 1–5 μm and 100 μm, respectively. The acicular crystals of cupromolybdite are typically combined in radiating aggregates. The mineral is associated with piypite, fedotovite, vergasovaite, hematite, magnetite, aphthitalite, langbeinite, palmierite, As-bearing orthoclase, lammerite, klyuchevskite, alumoklyuchevskite, euchlorine, lyonsite, pseudolyonsite, averievite, rutile and native gold. Cupromolybdite is honey-yellow or brown, and its acicular crystals are bright yellow. The mineral has yellow or light brown streak and an adamantine lustre. Cupromolybdite is brittle, and its fracture ranges from uneven to splintery. The calculated density is 4.512 g/cm 3 . The reflectance values ( R 1 and R 2 , %) in air for the four COM wavelengths are 14.95, 16.3 (470 nm), 13.4, 14.85 (546 nm), 12.73, 14.16 (589 nm), and 12.15, 13.5 (650 nm). The chemical composition (the mean of 7 electron microprobe analyses) of cupromolybdite is: CuO 43.03, FeO 0.08, ZnO 0.53, MoO 3 54.48, SO 3 0.71, V 2 O 5 0.28, SiO 2 0.04, total 99.15 wt%, corresponding, on the basis of 9 O atoms, to (Cu 2.83 Zn 0.03 Fe 0.01 ) ∑2.87 (Mo 1.98 S 0.05 V 0.02 ) ∑2.05 O 9 . The simplified formula of cupromolybdite is Cu 3 O(MoO 4 ) 2 = Cu 3 Mo 2 O 9 . Cupromolybdite is orthorhombic, space group Pnma , a = 7.6638(1), b = 6.8670(1), c = 14.5554(2) A, V = 766.01(2) A 3 and Z = 4. The strongest powder-diffraction lines [ d in A ( I ) ( hkl )] are: 7.312 (67) (002); 3.518 (55) (113); 3.436 (100) (020); 3.301 (99) (210, 104); 3.065 (79) (121); 2.556 (62) (220); 2.506 (66) (301, 024). The crystal structure was solved from single-crystal data and refined to R = 0.0314. Cupromolybdite is a natural analogue of the synthetic compound Cu 3 Mo 2 O 9 and the S-free analogue of vergasovaite, Cu 3 O[(Mo,S)O 4 ][SO 4 ]. The crystal structure of cupromolybdite contains strings of corner-shared Cu(1)O 6 octahedra elongated in the [010] direction. In cupromolybdite, the Cu(2)O 5 square pyramids and the Cu(3)O 6 distorted octahedra are linked to the Cu(1)O 6 octahedra of the strings by edges and to the MoO 4 and (Mo,S)O 4 tetrahedra by vertices. A minor admixture of S is concentrated in one of two independent tetrahedral positions. Cupromolybdite is named for its chemical composition.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. I. Yurmarinite, Na7(Fe3+,Mg,Cu)4(AsO4)6

Abstract A new mineral, yurmarinite, Na7(Fe3+,Mg,Cu)4(AsO4)6, 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, hematite, tenorite, tilasite and aphthitalite. Yurmarinite occurs as well-shaped, equant crystals up to 0.3 mm in size, their clusters up to 0.5 mm and thin, interrupted crystal crusts up to 3 mm × 3 mm on volcanic scoria. Crystal forms are {101}, {011}, {100}, {110} and {001}. Yurmarinite is transparent, pale green or pale yellowish green to colourless. The lustre is vitreous and the mineral is brittle. The Mohs hardness is ~4½. One direction of imperfect cleavage was observed, the fracture is uneven. D(calc.) is 4.00 g cm-3. Yurmarinite is optically uniaxial (-), ω = 1.748(5), ε = 1.720(3). The Raman spectrum is given. The chemical composition (wt.%, electron microprobe data) is Na2O 16.85, K2O 0.97, CaO 1.28, MgO 2.33, MnO 0.05, CuO 3.17, ZnO 0.97, Al2 O3 0.99, Fe2O3 16.44, TiO2 0.06, P2O5 0.12, V2O5 0.08, As2O5 56.68, total 99.89. The empirical formula, calculated on the basis of 24 O atoms per formula unit, is (Na6.55Ca0.28K0.22)∑7.05(Fe3+2.48Mg0.70Cu0.48Al0.23Zn0.14 Ti0.01Mn0.01)∑4.05(As5.94P0.02V0.01)∑5.97O24. Yurmarinite is rhombohedral, R3̅ c, a = 13.7444(2), c = 18.3077(3) Å, V = 2995.13(8) Å3, Z = 6. The strongest reflections in the X-ray powder pattern [d,Å (I)(hkl)] are: 7.28(45)(012); 4.375(33)(211); 3.440(35)(220); 3.217(36)(131,214); 2.999(30)(223); 2.841(100)(125); 2.598(43)(410). The crystal structure was solved from single-crystal X-ray diffraction data to R = 0.0230. The structure is based on a 3D heteropolyhedral framework formed by M4O18 clusters (M = Fe3+ > Mg,Cu) linked with AsO4 tetrahedra. Sodium atoms occupy two octahedrally coordinated sites in the voids of the framework. In terms of structure, yurmarinite is unique among minerals but isotypic with several synthetic compounds with the general formula (Na7-x⃞x)(M3+3+xM2+1-x)(T5+O4)2 in which T = As or P, M3+ = Fe or Al, M2+ = Fe and 0 ≤ x ≤ 1. The mineral is named in honour of the Russian mineralogist, petrologist and specialist in studies of ore deposits, Professor Yuriy B. Marin (b. 1939). The paper also contains a description of the Arsenathaya fumarole and an overview of arsenate minerals formed in volcanic exhalations.

Pseudolyonsite, Cu3(VO4)2, a new mineral species from the Tolbachik volcano, Kamchatka Peninsula, Russia

Pseudolyonsite, ideally Cu 3 (VO 4 ) 2 , is a new mineral from the medium-temperature fumaroles of the New Tolbachik scoria cones, Tolbachik volcano, Kamchatka Peninsula, Russia. It occurs as needles that are 5–20 μm across and up to 0.5 mm in the length, which sometimes produce parallel intergrowths, sprays or openwork clusters up to 2 mm. Associated minerals are: piypite, hematite, magnetite, lyonsite, aphthitalite, palmierite, langbeinite, filatovite, lammerite, vergasovaite, rutile and native gold. Pseudolyonsite is dark red with a brownish tint to black, translucent to opaque, with a reddish-brown streak and adamantine to semi-metallic lustre. The mineral is brittle, but thin long needles are flexible. The fracture is conchoidal, and no cleavage was observed. The calculated density is 4.749 g/cm 3 . In reflected light in air the mineral is grey with a weak bluish tint, non-pleochroic, has distinct anisotropy and ubiquitous red to orange internal reflections. The reflectance values (R 1 and R 2 , %) in air for the four COM wavelengths are, respectively, 17.05, 19.6 (470 nm); 16.1, 18.15 (546 nm); 15.85, 17.7 (589 nm); and 15.55, 17.4 (650 nm). Four electron probe (EDS) analyses produced the following mean values: V 2 O 5 40.37, CuO 48.83, ZnO 7.60, MoO 3 1.89, and SiO 2 0.14, total 98.83 wt%, which corresponds, on the basis of 8 O atoms, to (Cu 2.58 Zn 0.44 ) ∑3.02 (V 1.88 Mo 0.06 Si 0.02 ) ∑1.96 O 8 . The idealised formula is Cu 3 (VO 4 ) 2 . Pseudolyonsite is monoclinic: P 2 1 / c , a = 6.2695(4), b = 8.0195(3), c = 6.3620(3) A, β = 111.96(1)°, V = 296.66(3) A 3 , Z = 2. The strongest powder X-ray diffraction lines [ d in A (I) ( hkl )] are: 4.70 (60) (110); 3.30 (79) (021, 120); 3.22 (87) (111); 3.18 (34) (−121, −102); 2.894 (74) (200, −211); 2.761 (100) (012); 2.479 (59) (−212, −122); 2.419 (67) (031, 130). The crystal structure was solved from single-crystal data and refined to R = 0.0444. Pseudolyonsite is isostructural with synthetic monoclinic Cu 3 (VO 4 ) 2 . The crystal structure of pseudolyonsite contains corrugated octahedral layers formed by the chains of edge-shared, distorted Cu(2)-octahedra running along the c axis and connected to each other by distorted Cu(1)-octahedra. The octahedra of both types contain Cu and subordinate Zn, and they are typically Jahn-Teller-distorted. Adjacent octahedral layers are connected to each other by VO 4 tetrahedra. Pseudolyonsite is dimorphous with triclinic mcbirneyite. The name pseudolyonsite comes from its close visual similarity to another vanadate mineral, lyonsite, Cu 3 Fe 3+ 4 (VO 4 ) 6 . Both the mineral and its name have been approved by the IMA CNMNC (IMA No. 2009-062).

Crystal structure of larnite β-Ca2SiO4 and specific features of polymorphic transitions in dicalcium orthosilicate

The crystal structure of larnite, a natural analog of synthetic β-Ca2SiO4, has been determined: a = 5.5051(3) Å, b = 6.7551(3) Å, c = 9.3108(5) Å, β = 94.513(4)o, sp. gr. P21/n, Z = 4, and R1 = 0.0532 for 1071 reflections with I > 2σ (I). Larnite was found in skarn xenoliths (Lakargi, Kabardino-Balkaria, Russia). The mineral structure is based on a heteropolyhedral glaserite-like framework of interconnected Ca polyhedra and isolated [SiO4] tetrahedra. Based on an analysis of the layer-by-layer packing of atoms in the structures of larnite and other Ca2SiO4 polymorphs, the structural features and mechanisms of transitions from high-temperature (α, α′L, and α′H) to low-temperature (β and γ) Ca2SiO4 modifications, as well as their relationship with natural glaserite-like orthosilicates (merwinite Ca3Mg[SiO4]2 and bredigite Ca7Mg[SiO4]4), have been considered. The most likely atomic arrangement in hypothetical Ca2SiO4 models has been calculated by the method of atomistic potentials.

Tumchaite Na2(Zr,Sn)Si4O11·2H2O—A new mineral from carbonatites of the Vuoriyarvi alkali-ultrabasic massif, Murmansk Region, Russia

Abstract Tumchaite, Na2(Zr,Sn)Si4O11·2H2O, is a new species from the Vuoriyarvi alkali-ultrabasic massif, Murmansk Region, Russia, where it occurs as colorless to white tabular monoclinic crystals associated with calcite, dolomite, a mineral of the serpentine group and pyrite in the late dolomitecalcite carbonatites. It is transparent to translucent; with vitreous luster; and perfect cleavage on (100). Mohs hardness is 4.5, Dmeas is 2.78 (2) g/cm3. Tumchaite is optically biaxial (-), with α = 1.570 (2), β = 1.588 (2), γ = 1.594 (2), 2Vmeas = 60 (5)°, and elongation positive, Y = b, c ∧ Z = 3°. Pleochroism exists, with Y = Z = colorless, X = greenish-gray. Electron microprobe analysis gave (wt%): Na2O 13.72, CaO 0.15, SiO2 52.71, TiO2 0.35, ZrO2 20.41, SnO2 5.73, HfO2 0.60, H2O (computed assuming 2H2O pfu.) 7.86, total 101.53. The X-ray study pointed to space group P21/c, a = 9.144 (4), b = 8.818 (3), c = 7.537 (3) Å, β = 113.22 (3)°, V = 558.49 Å3, Z = 2. The strongest lines of the powder diffraction pattern [d in Å (I) (hkl)] are: 8.40 (10) (100), 5.38 (9) (111̅), 4.00 (8) (111), 3.401 (9) (202̅), 2.902 (9) (211), 2.691 (9) (131̅). The crystal structure of tumchaite was refined to R = 0.043 for 865 Fo > 4σ(Fo). The mineral is isotypic with penkvilksite-1M. The structure is characterized by silicate sheets parallel (100), formed by alternating clockwise- and counterclockwise-growing spiral chains of corner-sharing SiO4 tetrahedra. The sheets are connected by octahedra occupied by (Zr, Sn) at 0, 1/2, 0. The Zr/Sn ratio in the octahedra is 4. Water molecules and Na cations are placed in the cavities of the polyhedral framework. The ideal crystal-chemical formula is Na2 (Zr0.8Sn0.2)[Si4O11]·2H2O. The mineral is named tumchaite for the river Tumcha near Vuoriyarvi massif.

Fluorcalciobritholite, Ca,REE)5[(Si,P)O4]3F, a new mineral: description and crystal chemistry

The new mineral fluorcalciobritholite, ideally Ca 3 Ce 2 (SiO 4 ) 2 (PO 4 )F, has been found at Mount Kukisvumchorr, Khibiny alkaline complex, Kola Peninsula, Russia, in veinlets which contains aggregates of orthoclase, nepheline, sodalite and biotite in association with grains of fayalite, gadolinite-(Ce), zircon, monazite-(Ce), zirconolite (“polymignite”), fluorapatite, fluorite, molybdenite, lollingite and graphite. Fluorcalciobritholite forms long-prismatic hexagonal crystals up to 0.5 x 10 mm; the main crystal form is the hexagonal prism {10–10}. The mineral is transparent, with a pale pinkish to brown colour and a white streak. The hardness (Mohs) is 5.5, and the observed density is 4.2(1) g/cm 3 . Optically, it is uniaxial (−) with ω 1.735(5), e 1.730(5). Electron microprobe gave the following empirical formula based on [Si+P+S] = 3 apfu : [Ca 2.80 (Ce 0.93 La 0.54 Nd 0.26 Y 0.18 Pr 0.08 Sm 0.03 Gd 0.03 Dy 0.02 Yb 0.02 Er 0.01 ) ∑2.12 Th 0.04 Mn 0.03 Sr 0.02 ] ∑4.99 [(Si 1.94 P 1.06 ) ∑3 O 12 ] [F 0.76 O 0.22 Cl 0.01 ] ∑0.99 (Z = 2). The IR spectrum of metamict fluorcalciobritholite from Siberia showed a marked similarity with those of hydroxylbritholite-(Ce) and hydroxylbritholite-(Y). The strongest lines of the X-ray powder pattern [ d in A ( I ) ( hkl )] are: 3.51 (45) 002, 3.15 (70) 102, 2.85 (100) 211, 121, 2.78 (60) 300. The mineral is hexagonal, space group P 6 3 / m , with a = 9.580(7), c = 6.985(4) A, V = 555.2(7) A 3 . The crystal structure was refined from single-crystal X-ray diffraction data to R F = 0.029. Fluorcalciobritholite, whose simplified formula is (Ca,REE) 5 [(Si,P)O 4 ] 3 F, differs from fluorbritholite in having Ca > ∑REE, and differs from fluorapatite in having Si > P. Its compositional field falls within the limits Ca 2.5 REE 2.5 (SiO 4 ) 2.5 (PO 4 ) 0.5 F (boundary with fluorbritholite) and Ca 3.5 REE 1.5 (SiO 4 ) 1.5 (PO 4 ) 1.5 F (boundary with fluorapatite). Both the mineral and its name have been approved by the IMA Commission on New Minerals and Mineral Names.

The crystal structure and refined formula of mountainite, KNa2Ca2[Si8O19(OH)] · 6 H2O

Abstract Mountainite was described as a new mineral in 1957 with formula (Ca,Na2,K2)16Si32O80 · 24 H2O; its crystal structure was not solved up to now. We studied the structure of mountainite from the Yubileinaya pegmatite, Lovozero alkaline complex, Kola Peninsula, Russia. Mountainite is monoclinic, P2/c, a = 13.704(2), b = 6.5760(10), c = 13.751(2) Å, β = 105.752(10)°, V = 1192.7(3) Å3, Z = 2, Dcalc = 2.28 g/cm3. The crystal structure was solved by direct methods and refined to R(F) = 0.0639 for 1186 unique reflections with I > 3σ(I). Rietveld refinement on powder data completely confirmed the model obtained using a single crystal. Mountainite is a phyllosilicate, representative of a new structure type. The most specific feature of the mountainite structure is a TOT block formed by two SiO-layers [Si8O18(O,OH)2] (T-layers) and zig-zag columns of edge-sharing CaO5(H2O) octahedra sandwiched between them (O-layer). K cations occupy 10-fold polyhedra and are located between the columns of Ca-centered octahedra. The interlayer space between the neighboring TOT blocks is filled by Na cations and H2O molecules. The crystal-chemical formula is: KNa2Ca2{Si8O18[O(OH)]} · 6 H2O, the simplified formula is: KNa2Ca2Si8O19(OH) · 6 H2O.

Crystal structures of potassium-exchanged forms of catapleiite and hilairite

The crystal structures of potassium-exchanged forms of catapleiite and hilairite of the compositions (K0.49Ca0.42Na0.26)ZrSi3O9 · 2[(H2O)0.8(H3O)0.2] and K0.51ZrSi3O9 · 3[(H2O)0.5K0.27(H3O)0.23], respectively, were studied by X-ray diffraction and IR spectroscopy. Both structures retain the heteropolyhedral frameworks of the parent minerals formed by Zr octahedra and Si tetrahedra. The K cations occupy different positions in these minerals. In K-exchanged catapleiite, K cations are located only in the position occupied by Na in the structure of the parent mineral. In the K-exchanged form of hilairite, K cations are not only involved in the Na position but also partially occupy the H2O position.

Yaroshevskite, Cu9O2(VO4)4Cl2, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract A new mineral, yaroshevskite, ideally Cu9O2(VO4)4Cl2, occurs in sublimates collected from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, hematite, tenorite, lyonsite, melanothallite, atlasovite, kamchatkite and secondary avdoninite, belloite and chalcanthite. Yaroshevskite forms isolated prismatic crystals, up to 0.1 × 0.15 × 0.3 mm in size, on the surface of euchlorine crusts. The mineral is opaque and black, with a reddish black streak and lustre between metallic and adamantine. Yaroshevskite is brittle, no cleavage was observed and the fracture is uneven. The Mohs hardness is ~3½ (corresponding to a mean VHN micro-indentation hardness of 172 kg mm-2) and the calculated density is 4.26 g cm-3. In reflected light, yaroshevskite is grey with a weak bluish hue. Pleochroism, internal reflections and bireflectance were not observed. Anisotropy is very weak. The composition (wt.%) determined by electron microprobe is: CuO 61.82, ZnO 0.53, Fe2O3 0.04, V2O5 31.07, As2O5 0.32, MoO3 1.56, Cl 6.23, O=Cl2 -1.41; total 100.16. The empirical formula, calculated on the basis of 20 (O + Cl) anions is (Cu8.80Zn0.07Fe0.01)Σ8.88 (V3.87Mo0.12As0.03)Σ4.02O18.01Cl1.99. Yaroshevskite is triclinic, space group P1̅, a = 6.4344(11), b = 8.3232(13), c = 9.1726(16) Å , α = 105.338(14), β = 96.113(14), γ = 107.642(1)º, V = 442.05(13) Å3 and Z = 1. The nine strongest reflections in the X-ray powder pattern [dobs in Å (I)(hkl)] are as follows: 8.65(100)(001); 6.84(83)(01̅1); 6.01(75)(100); 5.52(60)(1̅01); 4.965(55)(011); 4.198(67)(11̅1̅); 4.055(65)(110); 3.120(55)(021); 2.896(60)(211̅,003,2̅20). The crystal structure was solved by direct methods from single-crystal X-ray diffraction data and refined to R = 0.0737. The yaroshevskite structure is unique. It is based on corrugated layers made up of chains of edge-sharing flat squares with central Cu2+ cations [Cu(1), Cu(4) and Cu(5)]; neighbouring chains are connected via groups consisting of three Cu2+-centred squares [two Cu(3) and Cu(6)]. Neighbouring layers are connected via pairs of Cu(2)O4Cl five-coordinate polyhedra and isolated VO4 tetrahedra. The structure of yaroshevskite can also be considered in terms of oxygen-centred tetrahedra: O(7)Cu4 tetrahedra are connected via common Cu(4) and Cu(5) vertices to form pyroxene-like chains [O2Cu6]∞. In this context, the structural formula can be written Cu3[O2Cu6][VO4]4Cl2. The mineral name honours the Russian geochemist Alexei A. Yaroshevsky (b. 1934) of Moscow State University.

Koksharovite, CaMg2Fe3+ 4(VO4)6, and grigorievite, Cu3Fe3+ 2Al2(VO4)6, two new howardevansite-group minerals from volcanic exhalations

Two new howardevansite-group minerals were discovered in the exhalations of fumaroles related to two volcanoes in Kamchatka, Russia. Koksharovite, CaMg2Fe 3þ 4(VO4)6, is found at the Bezymyannyi volcano in association with bannermanite. Grigorievite, Cu3Fe 3þ 2Al2(VO4)6, associated with bannermanite, ziesite, hematite, etc., was found at the Second scoria cone of the NorthernBreakthroughoftheGreatTolbachikFissureEruption,Tolbachikvolcano.Koksharoviteoccursasequanttoprismaticcrystals upto30 � 70mm.Itistranslucent,yellowish-browntoreddish-brownwithanadamantinelustre.Grigorieviteformsprismatic totabular crystals up to 40 � 100 mm. It is opaque, black with a semi-metallic lustre. Both minerals are brittle. The VHN hardness is 368 and 489 kg mm � 2 , the calculated density (Dcalc) 3.39 and 3.67 g cm � 3 for koksharovite and grigorievite, respectively. In reflected light, koksharovite is light grey, grigorievite is grey; both minerals are weakly anisotropic. Reflectance values (koksharovite//grigorievite: Rmax-Rmin ,%( l, nm)) are: 15.3-14.4//16.8-16.4 (470), 14.1-13.2//15.9-15.5 (546), 13.8-13.0//15.3-14.9 (589), 13.4-12.7//14.8-14.1 (650). Chemical data (wt%, electron-microprobe analysis; first value is for koksharovite, second for grigorievite) are: Na2O 0.76, 0.00; K2O 0.05, 0.00; MgO 9.43,2.78; CaO 3.57, 0.95; MnO 0.46,0.04;CuO 0.00,17.70; NiO 0.11, 0.00;ZnO 0.00,0.14; Al2O3 3.04,11.76; Fe2O3 23.88, 10.10; TiO2 2.42, 1.47; SiO2 0.20, 0.00; P2O5 0.98, 0.13; V2O5 53.86, 54.97; total 98.76, 100.04. The empirical formulae, based on 24 O atoms per formula unit, are: Na0.24K0.01Ca0.63Mg2.30Mn0.06Ni0.01Al0.59Fe 3þ 2.94Ti0.30Si0.03P0.14V5.83O24 (koksharovite); Ca0.17Mg0.69Mn0.01Cu2.23Zn0.02Al2.31Fe 3þ 1.27Ti0.18P0.02V6.05O24(grigorievite).Bothmineralsaretriclinic,spacegroupP-1,Z ¼1.Unit-