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Ovkun A.B.,Moscow State University | Indi L.B.,CNR Institute of Geosciences and Earth Resources | Aranin V.G.,Fersman Mineralogical Museum | Itvin Y.L.,Institute of Experimental Mineralogy
Mineralogical Magazine | Year: 2013

Kudryavtsevaite, ideally Na3MgFe3+Ti 4O12, is a new mineral from kimberlitic rocks of the Orapa area, Botswana. It occurs as rare prismatic crystals, up to 100 mm across, associated with Mg-rich ilmenite, freudenbergite and ulvospinel. Kudryavtsevaite is opaque with a vitreous lustre and shows a black streak. It is brittle; the Vickers hardness (VHN100) is 901 kg mm-2 (range: 876-925) (Mohs hardness ∼6). In reflected light, kudryavtsevaite is moderately bireflectant and very weakly pleochroic from dark grey to a slightly bluish grey. Under crossed polars, it is very weakly anisotropic with greyish-bluish rotation tints. Internal reflections are absent. Reflectance values (%), Rmin and Rmax, are: 21.3, 25.4 (471.1 nm), 20.6, 24.1 (548.3 nm), 20.0, 23.5 (586.6 nm) and 19.1, 22.4 (652.3 nm). Kudryavtsevaite is orthorhombic, space group Pnma, with a = 27.714(1), b = 2.9881(3), c = 11.3564(6) Å, V= 940.5(1) Å3, and Z= 4. The crystal structure [R1 = 0.0168 for 819 reflections with I> 2σ(I)] consists of edge-sharing and corner-sharing chains composed of Mg, Fe3+ and Ti atoms coordinated by six atoms of oxygen and running along the b axis, with Na filling the tunnels formed by the chains. The eight strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 7.17 (100) (301), 4.84 (70) (302), 2.973 (35) (901), 2.841 (50) (004), 2.706 (50) (902), 2.541 (50) (312), 2.450 (70) (611), and 2.296 (45) (612). The average results of 12 electron microprobe analyses gave (wt.%): Na2O 16.46(15), CaO 1.01(3), MgO 5.31(5), Fe2O3 22.24(32), Cr2O3 1.05(6), Al2O3 0.03(2), TiO2 53.81(50), total 99.91, corresponding to the empirical formula (Na2.89Ca0.10) Σ2.99(Ti3.67Fe3+ 1.52Mg 0.72Cr0.08)Σ, or ideally Na3MgFe 3+Ti4O12. The new mineral has been approved by the IMA-CNMNC and named for Galina Kudryavtseva (1947-2006), a well known Russian mineralogist and founder of the Diamond Mineralogy Laboratory and scientific school for investigation of diamond mineralogy and geochemistry at the Lomonosov State University in Moscow, Russia. © 2013 The Mineralogical Society.

Pekov I.V.,Moscow State University | Zubkova N.V.,Moscow State University | Husdalsdal T.A.,Veslefrikk 4 | Kononononkova N.N.,RAS Institute of Chemistry | And 3 more authors.
Canadian Mineralogist | Year: 2012

Carlgieseckeite-(Nd), ideally NaNdCa 3(PO 4)3F, a new mineral species of the belovite group of the apatite supergroup, was found at the Kuannersuit Plateau, Ilímaussaq alkaline complex, South Greenland. It is associated with albite, analcime and fluorapatite in cavities of an albite vein cross-cutting augite syenite. Carlgieseckeite-(Nd) forms hexagonal tabular crystals up to 0.25 × 1 × 1.3 mm, and their parallel intergrowth up to 0.7 × 1.3 mm is found epitactically overgrown on prismatic crystals of fluorapatite. A phase with the idealized formula Na1.5Nd1.5Ca2(PO4)3F epitactically overgrows some crystals of carlgieseckeite-(Nd). Carlgieseckeite-(Nd) is transparent and shows a distinct color-change effect, from almost colorless with a greenish hue in daylight to pink in yellow electric light. The luster is vitreous. The Mohs hardness is ca. 5. The mineral is brittle with no observed cleavage and an uneven fracture. The calculated density is 3.91 g/cm 3. Carlgieseckeite-(Nd) is optically negative, uniaxial [v = 1.655(3), ? = 1.632(2)] or shows anomalous biaxiality [a 1.632(2), b 1.654(3), g 1.656(3), 2V(meas.) 15(5)°]. The average chemical composition (electron-microprobe data) is: Na2O 5.68, CaO 18.53, SrO 7.55, BaO 0.14, La2O 3 1.32, Ce2O 3 10.60, Pr 2O 3 2.62, Nd 2O 3 15.08, Sm 2O 3 2.89, Gd2O 3 0.52, SiO 2 0.56, P 2O 5 32.72, F 2.80, Cl 0.06, -O=(F,Cl)2 -1.19, total 99.88 wt.%. The empirical formula calculated on the basis of 13 O + F + Cl apfu is: Na 1.17Ca 2.11Sr 0.46Ba 0.01La 0.05Ce 0.41Pr 0.10Nd 0.57Sm 0.11Gd 0.02Si 0.06P 2.94O 12.05F 0.94Cl 0.01. Carlgieseckeite-(Nd) is trigonal, space group P3, a 9.4553(1), c 6.9825(1) Å, V 540.62(1) Å3, Z = 2. The crystal structure was refined from X-ray-diffraction data (single crystal, R = 0.0218). Carlgieseckeite-(Nd) is the isostructural Ca- and Nd-dominant analogue of belovite-(Ce) and belovite-(La). The strongest lines of the powder X-ray pattern [d in Å (I)(hkl)] are: 7.02(22)(001), 5.33(18)(101), 3.923(27)(111), 3.463(23)(002), 3.095(19)(210), 2.815(100)(211,112), 2.727(42)(300). The mineral is named in honor of Carl Ludwig Giesecke (1761-1833), a mineralogist and polar explorer, the pioneer researcher of the mineralogy of Greenland. The Levinson suffix modifier -(Nd) is appropriate to express the dominance of Nd over other REE in the mineral. The holotype material is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.

Pekov I.V.,Moscow State University | Yakubovich O.V.,Moscow State University | Massa W.,University of Marburg | Chukanov N.V.,RAS Institute of Problems of Chemical Physics | And 3 more authors.
Canadian Mineralogist | Year: 2010

Three old specimens, collected in the 19th century and now deposited in Fersman Mineralogical Museum, Moscow, are labeled as rhodizite from the Sarapulka, Shaitanka (both corype localities) and Alabashka granitic pegmatite fields, Central Urals, Russia. All are Cs-dominant (Cs > K) and must now be considered londonite. The crystal structure of londonite from Sarapulka was solved from single-crystal data collected at 193 K and refined to R - 0.0203. The mineral is cubic, space group P4̄3m, a 7.3149(7) Å. Its structure is based on a microporous quasi-framework formed by clusters of four edge-sharing A1O6 octahedra linked by BO4 and BeO4 tetrahedra. Both Cs+ and K+ are ordered in the cages of the quasi-framework. The very short Cs-K distance, 0.51(3) Å, prevents simultaneous occupancy of these positions in the same cage. The Be and K atoms are also separated by an unallowable short distance of 2.76(3) Å, and thus their contents are coupled. The solid-solution system between rhodizite (K-dominant), londonite (Cs-dominant) and the hypothetical K- and Cs-free analogue, (□H2O){Al4[Be4B 12O28]}, is complicated, with numerous coupled heterovalent substitutions. Taking into consideration chemical, structural and IR data, it can be presented as: (A,□, H2O)1(Al,Li) 4(Be,Li,Al,□)4(B,Be)12[O 28-x(OH,F)x] ,where A = K, Cs and x < 1; the species-defining elements are marked in bold. The rhodizite-londonite series is structurally related to pharmacosiderite- and sodalite-type compounds, The association of pharmacosiderite-type[Al4O4] clusters and a soldalite-type [B12O24] framework results in the formation of an original complex, [Al4O4B 12O24], in rhodizite and londonite.

Mills S.J.,University of British Columbia | Mills S.J.,Khan Research Laboratories | Kartashov P.M.,RAS Institute of Geology and Mineralogy | Ma C.,California Institute of Technology | And 4 more authors.
American Mineralogist | Year: 2011

Yttriaite-(Y), ideally Y2O3, is a new mineral (IMA2010-039) from the alluvial deposits of the Bol'shaya Pol'ya River, Subpolar Urals, Russia. The new mineral occurs as isolated crystals, typically cubo-octahedra <6 μm in size, embedded in massive native tungsten. Associated minerals include: copper, zircon, osmium, gold, and pyrite. The main forms observed are {100} and {111}. Due to the crystal size, physical properties could not be determined; however, the properties of synthetic Y 2O3 are well known. Synthetic Y2O3 crystals are colorless to white with a white streak; crystals are transparent with an adamantine luster, while massive Y2O3 is typically translucent with an earthy luster. Synthetic Y2O3 has a Vickers hardness of 653.91, which corresponds to 5.5 on the Mohs scale. Synthetic Y2O3 crystals have good cleavage on {111}. Yttriaite-(Y) is isotropic; the refractive index measured at 587 nm on synthetic Y2O3 is n = 1.931. The empirical chemical formula (mean of 4 electron microprobe analyses) calculated on the basis of 3 O is: Y 1.98Dy0.01Yb0.01O3. Yttriaite-(Y) is cubic, space group Ia3, with parameters a = 10.6018(7) Å, V = 1191.62(7) Å3, and Z = 16. The five strongest lines in the powder X-ray diffraction pattern (measured on synthetic Y2O3 using synchrotron radiation) are [dobs in Å (I) (hkl)]: 3.0646 (100) (222), 1.8746 (55) (440), 1.5984 (38) (622), 2.6537 (26) (400), and 4.3356 (14) (211). The mineral name is based on the common name for the chemical compound, yttria.

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