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Chukanov N.V.,RAS Institute of Problems of Chemical Physics | Pekov I.V.,Moscow State University | Rastsvetaeva R.K.,Institute of Crystallography | Aksenov S.M.,Institute of Crystallography | And 5 more authors.
European Journal of Mineralogy | Year: 2012

The new Mg-and F-dominant lamprophyllite-group mineral lileyite (IMA 2011-021) was found at the Löhley quarry, Üdersdorf, near Daun, Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany, and named for the old name of the type locality, Liley. Associated minerals are nepheline, leucite, augite, magnetite, fluorapatite, perovskite, götzenite. Lileyite is brown, translucent; streak is white. It forms platy crystals up to 0.1 × 0.3 × 0.5 mm in size and their clusters up to 1 mm across on the walls of cavities in an alkaline basalt. Lileyite is brittle, with Mohs hardness of 3-4 and perfect cleavage on (001). D calc is 3.776 g/cm 3. The new mineral is biaxial (+), α = 1.718(5), β = 1.735(5), γ = 1.755(5), 2V (meas.) = 75(15), 2V (calc.) = 86°. The IR spectrum is given. The chemical composition is (EDS-mode electron microprobe, mean of 5 analyses, wt%): SiO 2 28.05, BaO 26.39, TiO 2 18.53, Na 2O 6.75, MgO 4.58, FeO 4.48, CaO 2.30, SrO 2.23, MnO 1.44, K iO 1.41, Nb 2O 5 0.95, F 3.88, -O=F 2 -1.63; total 99.36. The empirical formula based on 18 anions is: Ba 1.50Sr 0.19K 0.26Na 1.89Ca 0.36Mn 0.18Mg 0.99Fe 0.54Ti 2.01Nb 0.06Si 4.06O 16.23F 1.77. The simplified formula is: Ba 2(Na,Fe,Ca) 3MgTi 2(Si 2O 7) 2O 2F 2. The crystal structure was solved using single-crystal X-ray diffraction data (R = 0.024). Lileyite is monoclinic, space group C2/m, α = 19.905(1), β = 7.098(1), c = 5.405(1) Å , β = 96.349(5) V =758.93(6) Å 3, Z = 2. The strongest lines of the powder diffraction pattern [d, Å (I, %) (hkl)] are: 3.749 (45) (31-1), 3.464 (76) (510, 311, 401), 3.045 (37) (51-1), 2.792 (100) (221, 511), 2.672 (54) (002, 601, 20-2), 2.624 (43) (710, 42-1). Type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, registration number 4106/1. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung. Source

Pekov I.V.,Moscow State University | Chukanov N.V.,RAS Institute of Problems of Chemical Physics | Zadov A.E.,NPP Teplokhim | Voudouris P.,National and Kapodistrian University of Athens | And 2 more authors.
Journal of Geosciences | Year: 2011

Agardite-(Nd), ideally NdCu6(AsO4)3(OH)6·3H2O, has been approved by the IMA Commission on New Minerals, Nomenclature and Classification as a new mineral species, a Nd-dominant analogue of agardite-(Y), -(La) and -(Ce), a member of the mixite group. The material considered as the holotype was found in the Hilarion Mine, Agios Konstantinos (Kamariza), Lavrion District, Attikí Prefecture, Greece. Agardite-(Nd) occurs as thin, acicular to hair-like crystals up to 0.5 mm long and up to 5 μm thick, elongate along [001], with hexagonal cross section. More commonly, agardite-(Nd), agardite-(Y) and/or agardite-(La) form rims (up to 3 μm thick) of zoned acicular crystals (up to 0.015 × 1.2 mm) with a core consisting of zálesíite. They are usually combined in sprays or radiating clusters up to 2 mm. Gradual compositional transitions among zálesíite, agardite-(Nd), agardite-(Y) and agardite-(La) are typical. The minerals of the agardite-zálesíite solid-solution system are associated here with zincolivenite, azurite, malachite and calcite in cavities of an oxidized ore mainly consisting of goethite and in cracks of supergene altered mica schist. Agardite-(Nd) is transparent, light bluish green, with white streak, and lustre vitreous in crystals and silky in aggregates. Crystals are brittle, cleavage is none observed, and fracture is uneven. Calculated density is 3.81 g/cm3. Optically, agardite-(Nd) is uniaxial positive, ω = 1.709-1.712, ε = 1.775-1.780. Pleochroism is strong: O = pale turquoise-coloured, E = bright green-blue. Chemical composition of agardite-(Nd) (averaged of 6 electron microprobe analyses, H2O by difference) is: CuO 42.63, ZnO 3.52, CaO 2.15, Y2O3 1.27, La2O3 2.16, Ce2O3 0.38, Pr2O3 0.79, Nd2O3 3.05, Sm2O3 0.32, Gd2O3 0.40, Dy2O3 0.31, As2O5 33.65, H2Ocalc. 9.37, total 100.00 wt. %. The empirical formula based on 3 As atoms is: [(Nd0.19La0.14Y0.12Pr0.05Gd0.02Ce0.02Sm0.02Dy0.02)ΣREE0.58Ca0.39]Σ0.97(Cu5.49Zn0.44)Σ5.93 (AsO4)3(OH)5.38·2.64H2O. Chemical data on other minerals of the agardite-zálesíite system from the Hilarion Mine are also given and discussed. Agardite-(Nd) is hexagonal, space group P63/m; unit cell parameters are: a = 13.548(8), c = 5.894(6) Å, V = 937(2) Å3, Z = 2. The strongest reflections of the X-ray powder diagram (d,Å-I[hkl]) are: 11.70-100[100]; 4.443-22[111, 120]; 3.545-18[211, 121]; 2.935-18[221, 400]; 2.695-13[112, 320, 230], 2.559-10[410], 2.453-30[212, 122, 231]. The type specimen is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow. Source

Pekov I.V.,Moscow State University | Chukanov N.V.,RAS Institute of Problems of Chemical Physics | Britvin S.N.,Saint Petersburg State University | Kabalov Y.K.,Moscow State University | And 6 more authors.
Mineralogical Magazine | Year: 2012

Hielscherite, ideally Ca3Si(OH)6(SO 4)(SO3)•11H2O, (IMA 2011-037) is the first ettringite-group mineral with essential sulfite. We have identified a continuous natural solid-solution series from endmember thaumasite, Ca 3Si(OH)6(SO4)(CO3)•12H 2O, to a composition with at least 77 mol.% endmember hielscherite. In this series, the SO3:CO3 ratio is variable, whereas the SO4 content remains constant. Compositions with more than 50 mol.% endmember hielscherite have only been found at Graulay quarry near Hillesheim in the western Eifel Mountains, Rhineland-Palatinate, where they occur with phillipsite-K, chabazite-Ca and gypsum in cavities in alkaline basalt. Sulfite-rich thaumasite has been found in hydrothermal assemblages in young alkaline basalts in two volcanic regions of Germany: it is widespread at Graulay quarry and occurs at Rother Kopf, Schellkopf and Bellerberg quarries in Eifel district; it has also been found at Zeilberg quarry, Franconia, Bavaria. Hielscherite forms matted fibrous aggregates up to 1 cm across and groups of acicular to prismatic hexagonal crystals up to 0.3 × 0.3 × 1.5 mm. Individual crystals are colourless and transparent with a vitreous lustre and crystal aggregates are white with a silky lustre. The Mohs hardness is 2-2½. Measured and calculated densities are D meas = 1.82(3) and D calc = 1.79 g cm-3. Hielscherite is optically uniaxial (-), ω = 1.494(2), ε = 1.476(2). The mean chemical composition of holotype material (determined by electron microprobe for Ca, Al, Si, and S and gas chromatography for C, H and N, with the S 4+:S6+ ratio from the crystal-structure data) is CaO 27.15, Al2O3 2.33, SiO2 7.04, CO2 2.71, SO2 6.40, SO3 12.91, N2O5 0.42, H2O 39.22, total 98.18 wt.%. The empirical formula on the basis of 3 Ca atoms per formula unit is Ca3(Si0.73Al 0.28)Σ1.01(OH)5.71(SO4) 1.00(SO3)0.62(CO3) 0.38(NO3)0.05•10.63H2O. The presence of sulfite was confirmed by crystal-structure analysis and infrared and X-ray absorption near edge structure spectra. The crystal structure of sulfite-rich thaumasite from Zeilberg quarry was solved by direct methods based on single-crystal X-ray diffraction data (R 1 = 0.064). The structure of hielscherite was refined using the Rietveld method (R w p = 0.0317). Hielscherite is hexagonal, P63, a = 11.1178(2), c = 10.5381(2) Å, V = 1128.06(4) Å3 and Z = 2. The strongest reflections in the X-ray powder pattern [(d, Å (I)(hkl)] are: 9.62(100)(010,100); 5.551(50)(110); 4.616(37)(012,102); 3.823(64)(112); 3.436(25)(211), 2.742(38)(032,302), 2.528(37)(123,213), 2.180(35)(042,402;223). In both hielscherite and sulfite-rich thaumasite, pyramidal sulfite groups occupy the same site as trigonal carbonate groups, with analogous O sites, whereas tetrahedral sulfate groups occupy separate positions. Hielscherite is named in honour of the German mineral collector Klaus Hielscher (b. 1957). © 2012 Mineralogical Society. Source

Pekov I.V.,Moscow State University | Levitskiy V.V.,Russian Minerals Co. | Krivovichev S.V.,Saint Petersburg State University | Zolotarev A.A.,Saint Petersburg State University | And 3 more authors.
European Journal of Mineralogy | Year: 2012

A new arsenite mineral species dymkovite, ideally Ni(UO2) 2(As3+O3)2·7H2O (IMA no. 2010-087), was found at the Belorechenskoye deposit, Adygea Republic, Northern Caucasus, Russia. It is a supergene mineral associated with rauchite, annabergite, and goethite in cavities of a dolomite vein with primary uraninite (pitchblende), nickeline, and gersdorffite. Dymkovite forms longprismatic, lath-shaped to acicular crystals (≤0.5 mm long, ≤0.05 mm thick), which are elongated along [010]. They are combined in sprays or open-work, chaotic groups up to 1.5 mm across; crusts up to 2 × 2 mm2 and up to 0.05-mm-thick also occur. Dymkovite crystals are transparent and bright yellow, whereas crusts are translucent and light yellow to light greenish-yellow. The luster is vitreous. The mineral is brittle, the Mohs' hardness is ca. 3. Cleavage was not observed. Dcalc is 3.806 g cm-3. Dymkovite is optically biaxial (-), α = 1.625(2), β = 1.735(5), γ = 1.745(3), 2Vmeas = 20(10)°, 2Vcalc. = 32°. Dispersion is strong, r > v. Pleochroism is strong: X = very pale yellowish-green, Y ≈ Z = light greenish yellow. In the IR spectrum, bands of As3+O3 anions are strong, whereas bands of As 5+O4 anions are very weak. The average chemical composition (electron microprobe) is (in wt%): MgO = 1.11, FeO = 0.24, NiO = 5.40, ZnO=0.23, As2O3=19.57, P2O 5=0.58,UO3=59.43,H2Ocalc=13.44, total=100.00. The empirical formula, calculated on the basis of 17 O apfu, is: (Ni0.69Mg0.26Fe0.03 Zn0.03) ∑1.01 U1.97(As3+ 1.88P 0.08)∑1.96O9.94•7.06H2O. Dymkovite is monoclinic, space group C2/m, a = 17.99(3), b = 7.033(7), c = 6.633(9)Å, b = 99.62(11)°, V = 827(3)Å3, Z = 2. The crystal structure was refined from single-crystal X-ray diffraction data (R 1 = 0.063). The structure is based upon the [(UO2)(As 3+O3)]- sheets formed by chains of edge-sharing [UO7] pentagonal bipyramids and (As3+O3) triangular pyramids, which are linked through hydrogen bonds involving disordered [Ni(H2O)6]2+ octahedra and additional H2O molecules in the interlayer. The strongest lines of the powder X-ray pattern [d in Å(I)(hkl)] are: 8.93(100)(200), 4.463(34)(111, 400), 3.523(23)(020), 3.276(21)(220), 3.008(26)(11-2), 2.846(27)(112, 221, 31-2). Dymkovite is a Ni-dominant, almost arsenate-free analogue of seelite, Mg(UO2)2[(As3+O 3)1.4(As5+O4)0.6] ·7H2O. The mineral is named in honor of the Russian mineralogist Yuriy Maksimovich Dymkov (b. 1926), a specialist in U mineralogy, the geology of U deposits, and problems of mineral formation, who was one of the first researchers of the U ores of the Belorechenskoye deposit. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung. Source

Pekov I.V.,Moscow State University | Zelenski M.E.,Russian Academy of Sciences | Zubkova N.V.,Moscow State University | Ksenofontov D.A.,Moscow State University | And 5 more authors.
American Mineralogist | Year: 2012

A new mineral krasheninnikovite, ideally KNa 2CaMg(SO 4) 3F, is found in the sublimates of an active fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with tenorite, thenardite, hematite, euchlorine, blödite, vergasovaite, and fluorophlogopite. Krasheninnikovite forms long-prismatic to acicular crystals up to 3 mm long and up to 20 μm thick. The crystals are combined in sheaf-like, radiating or open-work matted aggregates forming nests up to several cm 3 or crusts. Krasheninnikovite is transparent, colorless in individuals and white in aggregates. The luster is vitreous. The mineral is brittle; the thinnest needles are flexible and elastic. The Mohs hardness is 2/1/23. Cleavage was not observed. D meas is 2.68(1), D calc is 2.67 g/cm 3. Krasheninnikovite is optically uniaxial (-), ω = 1.500(2), ε = 1.492(2). The IR spectrum is unique. The chemical composition (wt%, electron microprobe data) is: Na 2O 15.48, K 2O 6.92, CaO 11.51, MgO 9.25, MnO 0.15, FeO 0.04, Al 2O 3 0.23, SO 3 53.51, F 3.22, Cl 0.16, -O=(F,Cl) 2 -1.39, total 99.08. The empirical formula, calculated on the basis of 13 (O+F+Cl) apfu, is: K 0.67Na 2.27Ca 0.93Mn 0.01Mg 1.04A l0.02(SO 4) 3.04F 0.76Cl 0.02O 0.06. Krasheninnikovite is hexagonal, space group P6 3/mcm, a = 16.6682(2), c = 6.9007(1) Å, V = 1660.36(4) Å 3, Z = 6. The strongest reflections of the X-ray powder pattern [d, Å I(hkl)] are: 4.286 22(121); 3.613 24(040); 3.571 17(221); 3.467 42(131); 3.454 43(002); 3.153 100(140), 3.116 22(022), 2.660 39(222), 2.085 17(440). The crystal structure was solved on a single crystal and refined on a powder sample by the Rietveld method, R wp = 0.0485. The krasheninnikovite structure is unique. It is based upon a heteropolyhedral pseudoframework consisting of CaO 6 octahedra, MgO 5F octahedra, and SO 4 tetrahedra; K and Na cations are located in cavities. Krasheninnikovite is named in honor of the Russian geographer, ethnographer, and naturalist S.P. Krasheninnikov (1711-1755), one of the first scientists who researched Kamchatka. The type specimen is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow. Source

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