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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.

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.

Aksenov S.M.,RAS Shubnikov Institute of Crystallography | Rastsvetaeva R.K.,RAS Shubnikov Institute of Crystallography | Chukanov N.V.,RAS Institute of Problems of Chemical Physics | Kolitsch U.,Mineralogisch Petrographische Abt. | Kolitsch U.,University of Vienna
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2014

Calcinaksite, KNa[Ca(H2O)][Si4O10], a new natural member of the litidionite group, was found in a calcic xenolith from alkaline basalt of the Bellerberg volcano, Eastern Eifel region, Rhineland-Palatinate, Germany. The crystal structure has been studied based on single-crystal X-ray diffraction data. Triclinic unit-cell parameters are: a = 7.021 (2), b = 8.250 (3), c = 10.145 (2) Å, α = 102.23 (2), β = 100.34 (2), γ = 115.09 (3)°, space group . The structure model was determined by the 'charge-flipping' method and refined to R = 0.0527 in anisotropic approximation using 3057 I > 3σ(I). Calcinaksite is a hydrous calcium-dominant litidionite-group mineral. The crystal structure of calcinaksite (like other litidionite-group minerals and related compounds) is based on a heteropoly-hedral framework and is characterized by the presence of several types of channels. Calcium forms distorted CaO5Ø (Ø = H2O) octahedra while Na forms NaO5 square pyramids. Nine-coordinated K atoms are located in a channel extending along [010]. Water molecules occupy a channel running along the [100] direction and are characterized by a rather high equivalent isotropic displacement parameter of 0.053 (2) Å2. In calcinaksite, there are three short distances between the water molecule and oxygen atoms, Ow⋯O3 [2.844 (5) Å], Ow⋯O9 [2.736 (4) Å] and Ow⋯Ow [2.843 (7) Å]. These distances correspond to three hydrogen bonds detected by IR data (the bands at 3340, 3170 and 3540 cm-1). © 2014 International Union of Crystallography.

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.

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