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Wierzbicka-Wieczorek M.,Friedrich - Schiller University of Jena | Kolitsch U.,Mineralogisch Petrographische Abt. | Kolitsch U.,University of Vienna
European Journal of Mineralogy | Year: 2013

Colourless crystals of the novel compound BaYb6(Si 2O7)2(Si3O10) were prepared using a high-temperature flux-growth technique in air. The crystal structure was solved and refined to R(F) = 2.50 %using single-crystal X-ray diffraction data collected at room temperature. The silicate is monoclinic, space group P21/m (Z = 2), with a = 5.5173(11), b = 27.260(6), c = 6.8150(14)Å, β = 106.73(3)°, V = 981.6(3) Å3. BaYb6(Si2O7)2(Si3O 10) represents the first silicate containing both (Si 2O7) and (Si3O10) groups in the ratio 2:1 and is isotypic with (NH4)Cd6(P 2O7)2(P3O10). Its framework topology is characterised by one horseshoe-shaped trisilicate (Si 3O10) group, two symmetrically equivalent (Si 2O7) groups with the Si-O-Si angle of 165.3° and staggered conformation, and zigzag chains of edge-sharing distorted YbO 6 octahedra (). The Ba atoms occupy narrow channels extending parallel to [100]. The topological features of BaYb 6(Si2O7)2(Si3O 10) are compared to those of other compounds containing mixed groups (M2O7) and (M3O10). A similarity to BaY4(Si2O7)(Si3O10) is pointed out. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

Wierzbicka-Wieczorek M.,Friedrich - Schiller University of Jena | Tobbens D.M.,Helmholtz Center Berlin | Kolitsch U.,Mineralogisch Petrographische Abt. | Kolitsch U.,University of Vienna | Tillmanns E.,University of Vienna
Journal of Solid State Chemistry | Year: 2013

Three new, isotypic silicate compounds, BaY4(Si 2O7)(Si3O10), SrYb 4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P21/m, with a=5.532(1)/5.469(1)/5.278(1), b=19.734(4)/19.447(4)/19.221(4), c=6.868(1)/6.785(1)/6.562(1) Å, β=106.53(3)/106.20(3)/106.50(3), V=718.8(2)/693.0(2)/638.3(2) Å3, R(F)=0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si3O 10 groups (Si-Si-Si=93.15-95.98), Si2O7 groups (Si-Obridge-Si=180, symmetry-restricted) and edge-sharing M(1)O 6 and M(2)O6 octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopic data of chemically and topologically related disilicates and trisilicates, including BaY2(Si3O10) and SrY2(Si 3O10). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods. © 2013 Elsevier Inc.

Mills S.J.,University of British Columbia | Kampf A.R.,Natural History Museum of Los Angeles County | Kolitsch U.,Mineralogisch Petrographische Abt. | Kolitsch U.,University of Vienna | And 2 more authors.
American Mineralogist | Year: 2010

New discoveries of kuksite, Pb3Zn3Te 6+P2O14, from the Black Pine mine, Montana, and Blue Bell claims, California, have enabled a detailed crystal-chemical study of the mineral to be undertaken. Single-crystal X-ray structure refinements of the structure indicate that it is isostructural with dugganite, Pb 3Zn3Te6+As2O14, and joëlbruggerite, Pb3Zn3(Sb5+,Te 6+)As2O13(OH,O). Kuksite from the Black Pine mine crystallizes in space group P321, with unit-cell dimensions a = 8.392(1), c = 5.204(1) Å, V = 317.39(8) Å3, and Z = 1 (R1 = 2.91% for 588 reflections [Fo > 4σF] and 3.27% for all 624 reflections), while Blue Bell kuksite has the unit cell a = 8.3942(5), c = 5.1847(4) Å, and V = 316.38(4) Å3 (R1 = 3.33% for 443 reflections [Fo > 4σF] and .73% for all 483 reflections). Chemical analyses indicate that solid-solution series exist between kuksite, dugganite, and joëlbruggerite. Raman spectroscopic and powder X-ray diffraction data are also presented for samples from both occurrences. The crystal structure of the chemically related species yafsoanite, (Ca,Pb)3Te2 6+Zn3O12, from the type locality (Delbe orebody, Kuranakh Au Deposit, Aldan Shield, Saha Republic, Russia), has been refined to R1 = 2.41% for 135 reflections [Fo > 4σF] and 3.68% for all 193 reflections. A garnet-type structure has been confirmed and significantly improves upon the results of an earlier structure determination.

Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Housley R.M.,California Institute of Technology | Bottrill R.S.,Mineral Resources Tasmania | And 2 more authors.
American Mineralogist | Year: 2012

The new mineral reynoldsite, Pb 2Mn 2 4+O 5(CrO 4), occurs at the Blue Bell claims, near Baker, San Bernardino County, California, U.S.A., and at the Red Lead mine, Dundas, Tasmania, Australia. At the Blue Bell claims, reynoldsite occurs in subparallel growths and divergent sprays of thin prisms with a square cross section. At the Red Lead mine, it occurs as thin rectangular blades. At both occurrences, crystals are small (≤0.2 mm), and ubiquitously and multiply twinned. At both deposits, reynoldsite formed as a secondary mineral derived from the weathering of primary minerals including oxides and sulfides in the presence of acidic groundwater. Reynoldsite is dark orange-brown to black in color and has a dark orange-brown streak. Its luster is subadamantine and its Mohs hardness is about 4 1/2. The mineral is brittle with irregular to splintery fracture and a poorly developed {001} cleavage. The calculated density is 6.574 g/cm 3 (Red Lead mine). The very high indices of refraction and dark color permitted only partial determination of the transmitted light optical properties. Electron microprobe analyses of Blue Bell and Red Lead reynoldsite provided the empirical formulas (based on nine O atoms): Pb 1.97Mn 2.01O 5(Cr 1.01O 4) and (Pb 2.07Sr 0.04) ∑2.11Mn 2.15O 5(Cr 0.87O 4), respectively. The strongest powder X-ray diffraction lines for Red Lead reynoldsite are [d(hkl)I]: 3.427(02̄1,110)52, 3.254(021,11̄2,121)85, 3.052(1̄1̄2,111, 02̄2̄,1̄03)100, 2.923(013,122)40, 2.5015(004,2̄11,130)47, 1.9818(01̄5,1̄05,202,23̄1)42, 1.7694(11̄5,13̄4,203, 1̄42,1̄3̄3)36, and 1.6368(2̄2̄3,04̄3,221,124, 22̄4)36. Reynoldsite is triclinic with space group P1̄ and unit-cell parameters: a = 5.0278(7), b = 7.5865(11), c = 10.2808(15) Å, α = 91.968(12), β = 99.405(12), γ = 109.159(10)°, V = 363.81(9) Å 3, and Z = 2 (for a Red Lead mine crystal). The crystal structure of reynoldsite (R 1 = 10.2% for 902 reflections with F o > 4σF for a Red Lead crystal) contains close-packed layers of edge-sharing Mn 4+O 6 octahedra parallel to {001}. These layers are composed of edge-sharing double chains of octahedra extending along [100], which in turn are linked to one another by sharing edges in the [010] direction. The thick interlayer region contains Pb 2+ cations and CrO 4 tetrahedra. The 6s 2 lone-electron pair of the Pb 2+ is stereochemically active, resulting in a one-sided Pb-O coordination arrangement. The structure bears strong similarities to those of the phyllomanganates, such as chalcophanite and birnessite.

Kolitsch U.,Mineralogisch Petrographische Abt. | Kolitsch U.,University of Vienna | Mills S.J.,Khan Research Laboratories | Miyawaki R.,National Museum of Science and Nature | Blass G.,Merzbachstrasse 6
European Journal of Mineralogy | Year: 2012

The new mineral ferriallanite-(La) (IMA 2010-066), ideally CaLaFe 3+ AlFe2+ (SiO4)(Si2O 7)O(OH), is a member of the epidote supergroup and the La analogue of ferriallanite-(Ce). It occurs as a single, thick, tabular {100} crystal (2 mm in its longest dimension) in a void of a sanidinite xenolith found in the In den Dellen pumice quarries, Niedermendig, Mendig, Laach Lake volcanic complex, Eifel Mountains, Rhineland-Palatinate, Germany. Ferriallanite-(La) is associated with sanidine, minor "biotite", magnetite, nosean (grey, rounded grains) and trace amounts of dark green clinopyroxene. It is black, translucent in very thin splinters, with a brown streak, vitreous lustre, no cleavage, irregular to conchoidal fracture, Mohs hardness of ca. 6, Dcalc. = 4.208 g cm-3 (for empirical formula) and Dx=4.099 g cm-3. Optically, it is biaxial negative, with α=1.791(5), β= 1.827(6), γ=1.845(5) (white light), 2Vα (calc.) = 69°. The mineral is non-fluorescent and shows strong pleochroism, X = pale brownish, Y = greyish brown, Z = dark red-brown; absorption Z > Y ≫ X, orientation unknown. Dispersion is weak and the sign could not be determined. Electron microprobe analysis yielded the empirical formula (based on 12 O atoms and 1 OH group pfu): Ca0.98(La0.47Ce0.41Th 0.08Nd0.02Pr0.02)∑1.00(Fe 3+ 0.81Al0.14)∑0.95Al 1.00(Fe2+ 0.47Mn0.28Ti 0.16Mg0.05)∑0.96[(Si0.93Al 0.05)∑0.98O4](Si2O 7)O(OH). Ferriallanite-(La) is monoclinic, space group P2 1/m, with a = 8.938(2), b = 5.789(1), c = 10.153(2) Å ,β = 114.54(3)°, V = 477.88(6) Å 3 (single-crystal data) and Z = 2. Strongest eight lines in the X-ray powder diffraction pattern are [d in Å (I) hkl]: 9.22 (19) 001; 7.96 (34) 1̄01; 3.53 (38) 2̄11; 2.92 (100) 3̄02, 1̄13; 2.72 (50) 120, 013; 2.63 (36) 3̄11; 2.16 (17) 221 and 1.639 (34) 1̄06, 4̄24. A single-crystal X-ray structure refinement [R1(F) = 0.0150] and a derivation of the M3 site population from the chemical-analytical data yielded the formula A1Ca1.00 A2(La0.49Ce0.42Ca0.09) M1(Fe0.58Al0.42)M2(Al 0.94Fe0.06)M3(Fe0.49Mn 0.29Ti0.17Mg0.05)∑1.00(SiO 4)(Si2O7)O(OH), in reasonably good agreement with the electron microprobe data. The site refinements clearly show that there is some minor Fe at the M2 site, in contrast to the formula calculated using currently recommended methods for members of the epidote supergroup. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

Ertl A.,Mineralogisch Petrographische Abt. | Ertl A.,University of Vienna | Baksheev I.A.,Moscow State University | Giester G.,University of Vienna | And 3 more authors.
European Journal of Mineralogy | Year: 2016

NaFe3+ 3 (Al4Mg2)(Si6O18)(BO3)3 (OH)3O, is a new mineral species of the tourmaline supergroup from the Darasun gold deposit (Darasun mine), Vershino-Darasunskiy, Transbaikal Krai, Eastern-Siberian Region, Russia (52°20'24"N, 115°29'23"E). Bosiite formed as a hydrothermal phase in a gold-bearing quartz-vein spatially related to the Amudzhikan-Sretensky subvolcanic K-rich granodiorite-porphyry intrusion. Ores of this deposit are enriched in sulfides (up to 60%). Bosiite is intimately associated with other tourmalines. The first tourmaline generation is bosiite, which is followed by a second generation of oxy-dravite and a third generation of dravite. Bosiite also coexists with quartz and pyrite; further associated minerals in the vein are gangue minerals (quartz, calcite, and dolomite), sulfides (pyrite, arsenopyrite, chalcopyrite, pyrrhotite, tetrahedrite, sphalerite, and galena) and native gold. Crystals of bosiite are dark brown to black with a pale-brown streak. Bosiite is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and cleavage. It has a measured density of 3.23(3) g/cm3 (by pycnometry) and a calculated density of 3.26(1) g/cm3. In planepolarized light, it is pleochroic, O = yellow-brown, E = red-brown. Bosiite is uniaxial negative, ω = 1.760(5), € = 1.687(5). The mineral is trigonal, space group R3m, a = 16.101(3), c = 7.327(2) A, V = 1645.0(6) A3. The eight strongest X-ray diffraction lines in the (calculated) powder pattern [d in A(I)hkl] are: 2.606(100)(50-1), 8.051(58)(100), 3.008(58)(3-1-2), 4.025(57)(4-20), 3.543(50)(10-2), 4.279(46) (3-11), 2.068(45)(6-1-2), 4.648(28)(300). Analysis by a combination of electron microprobe (EMPA), inductively coupled plasma mass spectrometry (ICP-MS), Mössbauer spectroscopic data and crystal-structure refinement results in the empirical structural formula: X (Na0:73Ca0:23-0:04) σ1:00 Y (Fe3+ 1:47Mg0:80Fe2+ 0:59Al0:13Ti4+0:01)σ3:00 Z (Al3:23Fe3+ 1:88Mg0:89)σ6:00 T (Si5:92Al0:08O18)σ 6:00 (BO3) 3 V (OH)3 W [O0:85(OH) 0:15]σ1:00 According to the IMA-CNMNC guidelines, the dominant valence at the Y site is 3+ and the dominant cation is Fe3+. To accommodate the disorder and allocating cations to the Z and Y sites, the recommended procedure leads to the optimized empirical formula (based on 31 O): X(Na0.73Ca0.23-0.04) Y(Fe3+ 2.40Fe2+ 0.59Ti4+ 0.01)Z(Al3.36Mg1.69Fe3+ 0.95) T(Si5.92Al0.08O18) (BO3)3 V(OH)3 W[O0.85 (OH) 0.15]. Bosiite, ideally NaFe3+ 3 (Al4Mg2)(Si6O18)(BO3)3 (OH)3O, is related to end-member povondraite, ideally NaFe3+ 3 (Fe3+ 4Mg2)(Si6O18)(BO3)3 (OH)3O, by the substitution ZAl4 → ZFe3+ 4. Further, bosiite is related to oxy-dravite, ideally Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3 (OH)3O, by the substitutions [6]Fe3+ 3 → [6]Al3. Bosiite is named after Dr. Ferdinando Bosi, researcher at the University of Rome La Sapienza, Italy, and an expert on the crystallography and mineralogy of the tourmaline-supergroup minerals and the spinels. © 2016 E. Schweizerbart'sche Verlagsbuchhandlung.

Four new alunite-type chromates, KSc3(CrO4)2(OH)6, KIn3(CrO4)2(OH)6, RbIn3(CrO4)2(OH)6, and AgIn3(CrO4)2(OH)6, have been prepared by mild hydrothermal synthesis at T = 220 °C as well-developed, thick tabular to pseudo-octahedral crystals with maximum dimensions between approximately 0.5 and 1 mm. The crystal structures were refined from single-crystal intensity data (MoKα X-radiation, CCD area detector, 293 K, 2θmax = 70°). The new members adopt the alunite parent structure-type (space group R3m, no. 166), with a = 7.763(1)/7.813(1)/7.817(1)/7.845(1), c = 17.575(3)/17.682(3)/18.075(3)/16.997(3) Å, V = 917.2(2)/934.8 (2)/956.5(2)/905.9(2) Å3 (Z = 3), and R(F) = 1.36 / 1.21 / 1.23 / 1.33%, respectively. The H atoms could be located in each compound. Hydrogen bonds are all within a very close range (O3⋯O1 = 2.959-3.020 Å). All alkali and Sc/In sites are fully occupied, and the alkali atoms do not show any positional disorder, unlike Ag which is distinctly off-origin in AgIn3(CrO4)2(OH)26. Average bond-lengths are as follows: [12]K-O = 3.003, [6]Sc-O = 2.106, [4]Cr-O = 1.653 Å (KSc member); [12]K-O = 3.000, [6]In- O = 2.145, [4]Cr-O = 1.653 Å (KIn); [12]Rb-O = 3.051, [6]In-O = 2.147, Cr-O = 1.653 Å (RbIn); and [9]Ag-O = 2.826, [6]In-O = 2.142, [4]Cr-O = 1.648 Å (AgIn). The origin and possible meaning of a small, but conspicuous residual-density peak at (0, 0, 0.5) in the In members is discussed. These chromates represent the first structurally characterized Sc and In members of the large alunite supergroup, and may serve as analogues in future studies of naturally occurring Fe or sulfate members. Alunite-type Cs analogues could not be synthesized hydrothermally, in agreement with the fact that no natural or synthetic Cs compounds with the alunite topology have been reported so far. Instead, the syntheses yielded orthorhombic CsSc(CrO4)2 [CsCr3+(Cr6+O4)2-type] and monoclinic CsIn(CrO4)2 [(NH4)Fe(CrO4)2-type].

Wierzbicka-Wieczorek M.,University of Vienna | Kolitsch U.,Mineralogisch Petrographische Abt. | Tillmanns E.,University of Vienna
European Journal of Mineralogy | Year: 2010

Five new mixed-framework trisilicates were synthesised using a high-temperature flux growth technique. Colourless, glassy plates of SrY 2Si3O10 crystallise in space group P1̄, with a = 6.757(1), b = 6.885(1), c = 9.273(2) Å , α = 72.42(3), β = 86.37(3), γ = 88.37(3)°, V = 410.38(12)Å 3, Z = 2. The main building units of the new structure type represented by SrY 2Si3O10 are slightly curved Si 3O10 trimers and Y2O11 dimers (composed of YO6 octahedra sharing an edge with YO7 polyhedra), which are further edge-connected to adjacent dimers to form twisted zigzag chains parallel to [010]. BaREE2Si3O10 (REE = Gd, Er, Yb, Sc) form colourless small prisms, pseudohexagonal plates or isometric crystals, and crystallise in space group P21/m, with respectively a = 5.435(1) / 5.389(1) / 5.377(1) / 5.273(1), b = 12.241(2) / 12.163(2) / 12.117(2) / 11.918(2), c = 6.932(1) / 6.840(1) / 6.790(1) / 6.591(1) Å , β = 106.26(3) / 106.47(3) / 106.50(3) / 107.06(3)°, V = 442.74(13) / 429.94(12) / 424.17(12) / 395.98(12) Å 3, Z = 2. BaREE2Si3O10 (REE = Gd, Er, Yb, Sc) are isotypic with BaY2Si3O10. Their topology is characterised by horseshoe-shaped trisilicate (Si3O10) groups and zigzag chains of edge-sharing distortedMO6 octahedra (M = Gd, Er, Yb, Sc). Correlations between β-, Si-Si-Si angle and unit-cell volume and REE3+ ionic radii are discussed. The geometries of the Si3O10 and T3O10 groups (T = Ge, P, As, Al, Ga, V) in non-silicates are briefly reviewed, with special focus on narrow Si-Si-Si angles. © 2009 E. Schweizerbart'sche Verlagsbuchhandlung.

Wierzbicka-Wieczorek M.,University of Vienna | Kolitsch U.,Mineralogisch Petrographische Abt. | Tillmanns E.,University of Vienna
Acta Crystallographica Section C: Crystal Structure Communications | Year: 2010

The title compound, dibarium digadolinium(III) tetra-silicate, crystallized from a molybdate-based flux. It represents a new structure type and contains finite zigzag-shaped C2-symmetric Si4O13 chains and Gd2O12 dimers built of edge-sharing GdO7 polyhedra. The [9+1]-coordinated Ba atoms are located in voids in the atomic arrangement. All atoms are in general positions except for one O atom, which lies on a twofold axis. The structure is compared with those of the few other known tetra-silicates. © 2010 International Union of Crystallography.

Kolitsch U.,Mineralogisch Petrographische Abt.
Mineralogical Magazine | Year: 2010

The previously unknown crystal structure of mckinstryite, originally described as Ag1.18Cu0.82S or (Ag,Cu)2S, was solved and refined using single-crystal X-ray diffractometer data collected from a sample from the Clara mine, Black Forest (Mo-Kα radiation, CCD area detector, R1(F) = 3.85%). Mckinstryite has the refined formula Ag 4.92Cu3.08S4 or Ag1.23Cu 0.77S (idealized Ag5Cu3S4 or Ag 1.25Cu0.75S) and crystallizes in space group Pnma (no. 62), with a = 14.047(3) Å, b = 7.805(2) Å, c = 15.691(3) Å , V = 1720.3(7) Å3, Z = 8. The structure contains five Ag, six Cu and eight S sites in the asymmetric unit. One of the Ag sites shows minor Cu-for-Ag substitution. The topology is based on flat, interrupted (010) layers of Cu and S atoms (all atoms on y = 0.25), in which the Cu atoms show triangular or two-coordination to S (interrupted {6,3} tiling). These layers alternate with uneven layers consisting of Ag atoms showing irregular three- to two-coordination to S. Some fairly short Ag - Cu contact distances (2.7810 -2.884 Å) strongly indicate that metal-metal interaction plays an important role in mckinstryite. The topology is related to that of stromeyerite (~AgCuS) which contains complete flat layers of Cu atoms triangularly coordinated to S atoms, alternating with layers of loosely packed Ag atoms. A critical evaluation of literature data on the chemical composition and unit-cell parameters of mckinstryite confirms the presence of a small compositional range of mckinstryite which extends approximately from Ag1.18Cu0.82S to Ag1.25Cu0.75S, with the presently studied sample being fairly Ag-rich. The accurate limits of this range at ambient temperature are still to be determined. © 2010 Mineralogical Society.

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