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Bodø, Norway

Bonazzi P.,University of Florence | Lepore G.O.,University of Florence | Bindi L.,University of Florence | Chopin C.,Ecole Normale Superieure de Paris | And 2 more authors.
American Mineralogist | Year: 2014

In yttrian fluorite from pegmatites of the Tysfjord granite, Norway, grayish-green to very pale green gatelite-like crystals occur along with millimeter-size aggregates of Y-silicates as a late primary phase; they are associated with allanite-(Ce), bastnäsite-(Ce), and intimately inter- or overgrown by törnebohmite-(Ce). Sub- to euhedral crystals, up to 400 ?m in size, are chemically zoned between two near-end-member compositions that imply the existence of two new members of the polysomatic gatelite group, in which ET polysomes are composed of E modules with epidote-type structure alternating with T modules of törnebohmite-type structure. The two new minerals form a continuous solid-solution series, along which two crystals of intermediate compositions served for species definition. Their electron-microprobe analyses yield the empirical formulas (Ca1.00Mn0.03Na 0.08La0.51 Ce1.30Pr0.16Nd 0.62Sm0.10Gd0.06Dy0.03Er 0.01Y0.06Th0.01)σ3.97 (Al 3.21Fe2+ 0.79)σ4.00Si 5.01O20(OH)2 for perbøeite-(Ce) [IMA 2011-55] and (Ca1.10Mn0.03Na0.20La0.42Ce 1.14Pr0.16Nd0.60Sm0.13Gd 0.07Dy0.03Er0.01Yb0.01Y 0.12Th0.02)σ4.04 (Al 3.54Fe2+ 0.40Mg0.02) σ3.96Si4.99O20(OH)2 for alnaperbøeite-(Ce) [IMA 2012-54]. The respective end-member formulas are A(Ce3Ca)M(Al3Fe2+)Si2O 7(SiO4)3O(OH)2, which requires Ce2O345.10, CaO 5.14, FeO 6.58, Al2O 3 14.01, SiO2 27.52, H2,O 1.65, total 100.00 wt%; and A(Ce2.5CaNa0.5)M(Al4)Si 2O7(SiO4)3O(OH)2, which requires Ce2O3 40.86, CaO 5.58, Na2O 1.54, Al2O3 20.31, SiO2 29.92, H2,O 1.79, total 100.00 wt%. Cell parameters of perbøeite-(Ce) and alnaperbøeite-(Ce) for these crystals are α = 8.9277(6) and 8.9110(4), β = 5.6548(6) and 5.6866(2), c = 17.587(1) and 17.5252(7) Å, β = 116.475(8) and 116.300(5)°, V = 794.8(1) and 796.13(7) Å3, respectively. Members of the perbøeite-(Ce)- alnaperbøeite-(Ce) solid solution are topologically identical to the minerals gatelite-(Ce) and västmanlandite-(Ce). Structural data (space group P21/m) were obtained for the holotype crystals and for several crystals with intermediate composition. Structural refinements of a crystal annealed step-wise in air confirm that most of Fe in M3 is divalent before heating and show that oxidation/dehydrogenation takes place mostly in the E module (M3 and H1). Perbøeite-(Ce) derives from gatelite-(Ce) by the homovalent substitution [M3Fe2+ → M3Mg]. Alnaperbøeite- (Ce) derives from perbøeite-(Ce) or gatelite-(Ce) by the coupled heterovalent substitutions [ANa+ + 2M3Al3+ → AREE + 2M3(Fe2+ or Mg)]. Törnebohmite-(Ce) associated with alnaperbøeite-(Ce) is Na-free, whereas coexisting allanite is Na-bearing and shows the same coupled substitution between A and M sites as the one relating perbøeite-(Ce) and alnaperbøeite-(Ce) (Na0.5Al ↔ REE0.5Fe2+). This could suggest, although crystallographic evidence is inconclusive, that Na incorporation in the ET polysome occurs in the E module alone (A2 or A1 sites), leading to the sodian E end-member A(CaREE0.5Na0.5)M(Al3)Si 2O7(SiO4)O(OH). In any event, this new epidote end-member is needed to account for up to ca. 10 mol% of the composition of allanite-group minerals, in which Na2O contents may reach 0.3 wt%. Sodium must be analyzed in epidote-supergroup and gatelite-group minerals. © 1997 - 2014 Mineralogical Society of America. All rights reserved. Source

Cooper M.A.,University of Manitoba | Husdal T.A.,Veslefrikk 4 | Ball N.A.,University of Manitoba | Abdu Y.A.,University of Manitoba | Hawthorne F.C.,University of Manitoba
Mineralogical Magazine | Year: 2013

Schluterite-(Y), ideally (Y,REE)2Al(Si2O7)(OH) 2F, is a new silicate mineral species from the Stetind pegmatite, Tysfjord, Nordland, Norway. It forms dense, fibrous, radiating aggregates (up to ∼2 mm) diverging to individual needle-like crystals (up to ∼1 mm long) in cavities. Crystals are acicular to bladed, flattened on {001} and elongated along [010], and the dominant form is {001}. Schluterite-(Y) is transparent, pale pink with a white streak and a vitreous lustre, and does not fluoresce under short-wave ultraviolet light. Mohs hardness is 51/2-6, and schlüterite-(Y) is brittle with an irregular fracture, and has no cleavage. The calculated density is 4.644 g/cm3. The indices of refraction are a = 1.755, β = 1.760, y = 1.770, all ± 0.005, 2Vobs = 71.8 (5)°, 2Vcalc = 71°, non-pleochroic, optic orientation is X∧ a = 83.1° (β obtuse), Y//b, Z ∧ c = 50.3° (β acute). Schluterite-(Y) is monoclinic, space group P21/c, a 7.0722(2), b 5.6198(1), c 21.4390(4) Å, β 122.7756(3)°, V716.43(5) Å3, Z = 4. The seven strongest lines in the X-ray powder-diffraction pattern are as follows: [d (Å), I, (hkl)]: 4.769, 100, (012); 2.972, 55, (214); 3.289, 51, (112); 2.728, 49, (2̄16); 2.810, 37, (020); 3.013, 37, ((1̄16); 4.507, 36, (004). Chemical analysis by electron microprobe gave SiO2 22.64, Al2O3 9.45, Y 2O3 15.35, La2O3 3.25, Ce 2O3 9.69, Pr2O3 2.05, Nd 2O3 9.50, Sm2O3 3.57, Gd 2O3 4.65, Dy2O3 4.21, Er 2O3 2.31, Yb2O3 1.86, F 2.71, H 2Ocalc 3.78, O = F -1.14, sum 93.88 wt%. The H 2O content was determined by crystal-structure analysis. On the basis of 10 anions with (OH) + F = 3 a.p.f.u. (atoms per formula unit), the empirical formula is (Y 0.73 Ce 0.32 Nd 0.30 Gd 0.14 Dy 0.12 La 0.11 Sm 0.11 Pr 0.07 Er 0.06 Yb 0.05)Σ=2.01 Al0.99 Si2 01 O 7(OH)2 24 F0.76. The crystal structure of schluterite-(Y) was solved by direct methods and refined to an R1 index of 1.8% based on 1422 unique observed reflections. In the structure of schluterite-(Y), Al(OH)4O2 octahedra share (OH)-(OH) edges to form [MΦ4] chains that are decorated by (Si2O7) groups that bridge O vertices of neighbouring octahedra in a staggered fashion on either side of the chain. These [Al(OH) 2(Si2O7)] chains extend parallel to b, and are linked into a continuous framework via bonds to interstitial [8](Y,REE) (= <2.400 Å;>) and [9](Y,REE) (= <2.548 Å>) atoms. © 2013 The Mineralogical Society. Source

Miyawaki R.,National Museum of Science and Nature | Yokoyama K.,National Museum of Science and Nature | Husdal T.A.,Veslefrikk 4
European Journal of Mineralogy | Year: 2013

Bastnasite-(Nd), ideally (Nd,La,Ce)(CO3)F, occurs in the Stetind pegmatite, Tysfjord, Nordland, Norway, in association with bastnasite-(Ce), calcioancylite-(Nd) and/or kozoite-(Nd), stetindite, vyuntspakhkite-(Y) and Y-bearing fluorite. It forms 20 mm wide zones in outer parts of tabular bastnasite-(Ce) crystals. Bastnasite-(Nd) is translucent and is pale purplish pink to colourless with a vitreous, greasy or pearly lustre. Bastnasite-(Nd) has a Mohs hardness of 4-4, is brittle, and shows an indistinct cleavage on {1010} and an uneven fracture. The calculated density and mean refractive index are 5.23 g cm3 and 1.76, respectively. It is hexagonal, space group P6 2c, a = 7.0792(13), c = 9.721(2) , V = 421.92(18) 3 and Z = 6. The five strongest lines in the powder XRD pattern are [d(A° ), I/I0, hkl]: 4.86, 71, 002; 3.54, 70, 110; 2.86, 100, 112; 2.04, 31, 300 and 2.00, 48, 114. The electron-microprobe analyses lead to the empirical formula (on the basis of M = C = 1 apfu): Nd0.353La0.253Ce0.251Pr0.086Sm0.037Gd0.016Y0.004Dy0.001CO2.978F1.044. Bastnasite-(Nd) is a member of the bastnasite group, and is the Nd-dominant analogue of bastnasite-(Ce), bastnasite-(La) and bastnasite-(Y). Bastnasite-(Nd) formed as a late phase in cavities in Y-bearing fluorite, which in turn is a late formation of the pegmatite. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung. Source

Malcherek T.,University of Hamburg | Mihailova B.,University of Hamburg | Schluter J.,University of Hamburg | Husdal T.,Veslefrikk 4
European Journal of Mineralogy | Year: 2012

The title mineral has been discovered in a granitic pegmatite at the Stetind quarry, Tysfjord, Norway. Atelisite-(Y) forms pale brown to colourless, transparent crystals of dipyramidally terminated, short-prismatic habit with a diameter of up to 0.3 mm. Based on electron microprobe analysis and 16 anions per formula unit, the empirical formula is (Y3.11Yb 0.46Er0.19Dy0.11 Gd0.09Ho 0.01Tb0.02)Σ3.99Si2.40O16H10.43. The presence of hydroxyl-groups is inferred from the detection of OH-stretching modes near 3225 cm∼ in Raman spectra of the new mineral. The crystal structure of atelisite was solved and refined on single-crystal X-ray diffraction data in space group I42d, with a = 6.947(4), c = 6.133(3) Å,V= 295.98(28) Å3. Site occupancy refinement at the 4a-site approaches 3/4 Si-occupancy, if the 4b-site is fully occupied by Y and Yb, with a refined Y/Yb ratio of 4. This suggests an idealized formula of Y 4Si3O8(OH)8 for atelisite-(Y). The crystal structure of the new mineral is of particular interest with regard to the known occurrence of hydrous species in the nominally anhydrous minerals xenotime and zircon. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung. Source

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. Source

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