Description and crystal structure of vajdakite, [(Mo6+O2)2(H2O)2 As3+ 2O5]·H2O—A new mineral from Jáchymov, Czech Republic
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Petr Ondruš
,
Roman Skála
Abstract
Vajdakite, a new mineral from Jáchymov, NW Bohemia, Czech Republic, forms minute acicular, gray-green crystals associated with arsenolite, scorodite, parascorodite, kanˇkite, annabergite, köttigite, pyrite, marcasite, nickelskutterudite, and löllingite. Microprobe analysis gave (in wt%): As = 27.72, Mo = 35.39, O = 36.66, total = 99.77. The simplified chemical formula is [(Mo6+O2)2(H2O)2 As3+2O5]·H2O. The mineral is monoclinic, P21/c, a = 7.0515(6), b = 12.0908(9), c = 12.2190(14) Å, b = 101.268(9)°, V = 1021.7(2) Å3, Z = 4, Dmeas = 3.50(2) g/cm3, and Dcalc = 3.509 g/cm3. The strongest lines in the powder X-ray diffraction pattern d(I)(hkl) are: 6.046 (100)(020), 3.324 (59)(023), 6.915 (26)(100), 2.264 (19)(310), 3.457 (16)(200), 2.624 (15)(230), and 3.819 (10)(031). Vajdakite is optically positive, with X || b and Z . c =12; elongation is positive. Its birefrigence is 0.28, with 2Vcalc = 35.1° nα = 1.757(2), nβ= 1.778(2), and nγ = 2.04(1). The pleochroic scheme is X ~ Y = light greenish gray, and Z = yellowish gray. Crystal size varies between 0.1 to 0.5 mm. TG curve and IR spectra show that vajdakite contains two distinct types of water molecules. The crystal structure was solved by direct methods (MoKα radiation) and refined using 1787 unique reflections to R = 0.0455, Rw = 0.1143. There are double chains built up by two individual chains with a sequence -O-As-OMo- interconnected by oxygen atoms from two triangular AsO3 groups and two structurally nonequivalent MoO5(H2O) octahedra. The two vertex-sharing, triangular AsO3 groups form an (As2O5)4- diarsenite group. The first type of water molecule is not included in the coordination, but the second one is in octahedral coordination around Mo. The water molecules are linked by a complicated net of interlayer and intralayer hydrogen bonds
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
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- Discovery of clinoenstatite in garnet pyroxenites from the Dabie-Sulu ultrahigh-pressure terrane, east-central China
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Artikel in diesem Heft
- Thermal equations of state for B1 and B2 KCl
- Determination of molar absorptivities for infrared absorption bands of H2O in andesitic glasses
- H2O activity in H2O-N2 fluids at high pressure and temperature measured by the brucitepericlase equilibrium
- Kinetics of iron oxidation-reduction in hydrous silicic melts
- Kinetics of cation ordering in synthetic MgAl2O4 spinel
- Structural properties and heat-induced oxidation-dehydrogenation of manganoan ilvaite from Perda Niedda mine, Sardinia, Italy
- Ultrahigh-pressure metamorphism in western Tianshan, China: Part I. Evidence from inclusions of coesite pseudomorphs in garnet and from quartz exsolution lamellae in omphacite in eclogites
- Ultra-high pressure metamorphism in western Tianshan, China: Part II. Evidence from magnesite in eclogite
- Discovery of clinoenstatite in garnet pyroxenites from the Dabie-Sulu ultrahigh-pressure terrane, east-central China
- Ultrahigh-pressure (UHP) low-Al titanites from carbonate-bearing rocks in Dabieshan- Sulu UHP terrane, eastern China
- Metamictization and recrystallization of titanite: An infrared spectroscopic study
- Fine structure of infrared OH-stretching bands in natural and heat-treated amphiboles of the tremolite-ferro-actinolite series
- Correlation between OH concentration and oxygen isotope diffusion rate in diopsides from the Adirondack Mountains, New York
- The substitution Fe3+-Al and the isosymmetric displacive phase transition in synthetic zoisite: A powder X-ray and infrared spectroscopy study
- In situ X-ray observation of the reaction dolomite = aragonite + magnesite at 900–1300 K
- High-pressure single-crystal X-ray and powder neutron study of F,OH/OD-chondrodite: Compressibility, structure, and hydrogen bonding
- Quantitative characterization of biotic iron oxides by analytical electron microscopy
- Synthesis and NMR characterization (1H and 31P MAS) of the fluorine-free hydroxylapatite–britholite-(Y) series
- Quantum mechanical calculations of dioctahedral 2:1 phyllosilicates: Effect of octahedral cation distributions in pyrophyllite, illite, and smectite
- The nature of disorder in montmorillonite by simulation of X-ray powder patterns
- Ferripedrizite, a new monoclinic BLi amphibole end-member from the Eastern Pedriza Massif, Sierra de Guadarrama, Spain, and a restatement of the nomenclature of Mg-Fe-Mn-Li amphiboles
- Description and crystal structure of vajdakite, [(Mo6+O2)2(H2O)2 As3+ 2O5]·H2O—A new mineral from Jáchymov, Czech Republic
- Some remarks on fission-track observational biases and crystallographic orientation effects
- Surface reconstruction and As-polymerization at fractured loellingite (FeAs2) surfaces
- The strength of moissanite
- Diamond formation through carbonate-silicate interaction
- Anisotropic Fe-Mg diffusion in biotite
- Characterization of a high-pressure phase of silica from the Martian meteorite Shergotty
