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Galuskin E.V.,University of Silesia | Galuskin E.V.,University of Bern | Galuskin E.V.,German Aerospace Center | Kusz J.,University of Silesia | And 15 more authors.
Mineralogical Magazine | Year: 2012

New electron-microprobe analyses of mayenite from the Ettringer Bellerberg volcano near Mayen in the Eifel district, Germany have high Cl contents and Raman spectroscopy indicates the presence of OH groups. Neither of these components is included in the generally accepted chemical formula, Ca 12Al14O33. A refinement of the crystal structure by single-crystal X-ray methods reveals a previously unrecognized partial substitution. The O2 site which forms one of the apices of an AlO 4 tetrahedron (with 3 × O1 sites) is replaced by 3 × O2a sites, which change the coordination of the central Al atom from tetrahedral to octahedral. This substitution is related to partial hydration of Ca 12Al14O32Cl2 according to the isomorphic scheme (O2- + Cl-) → 3(OH)-. The revised composition of Eifel mayenite is best described by the formula Ca12Al14O32-xCl2-x(OH)3x (x ∼0.75); the original formula, Ca12Al14O 33, is inadequate. The analysed mineral can be considered to consist of endmember Ca12Al14O32Cl2 (62.5 mol.%) and endmember Ca12Al14O30(OH) 6 (37.5 mol.%). © 2012 Mineralogical Society.


Galuskin E.V.,University of Silesia | Kusz J.,University of Silesia | Armbruster T.,University of Bern | Galuskina I.O.,University of Silesia | And 3 more authors.
American Mineralogist | Year: 2013

Vorlanite (CaU6+)O4 [Fm3m, a = 5.3647(9) Å, V = 154.40(4) Å3, Z = 2] was found in larnite pyrometamorphic rocks of the Hatrurim formation at the Jabel Harmun locality, Judean Desert, Palestinian Autonomy. Vorlanite crystals from these larnite rocks are dark-gray with greenish hue in transmitted light. This color in transmitted light is in contrast to dark-red vorlanite [Fm3m, a = 5.3813(2) Å, V = 155.834(10)Å3, Z = 2] from the type locality Upper Chegem caldera, Northern Caucasus. Heating above 750 °C of dark-gray vorlanite from the Jabel Harmun, as well as dark-red vorlanite from Caucasus, led to formation of yellow trigonal uranate CaUO4. The unusual color of vorlanite from Jabel Harmun is assumed to be related to small impurities of tetravalent uranium.


Galuskin E.V.,University of Silesia | Galuskina I.O.,University of Silesia | Kusz J.,University of Silesia | Armbruster T.,University of Bern | And 3 more authors.
Mineralogical Magazine | Year: 2014

The new mineral species vapnikite, Ca3UO6, was found in larnite pyrometamorphic rocks of the Hatrurim Formation at Jabel Harmun in the Judean desert, Palestinian Autonomy, Israel. Vapnikite is an analogue of the synthetic ordered double-perovskite β-Ca3UO6 and is isostructural with the natural fluorperovskite - cryolite Na3AlF 6. Vapnikite Ca3UO6 (P21/n, Z = 2, a = 5.739(1), b = 5.951(1), c = 8.312(1) Å , β = 90.4(1)°, V = 283.9(1) Å 3) forms yellow-brown xenomorphic grains with a strong vitreous lustre. Small grains up to 20-30 μm in size are wedged between larnite, brownmillerite and ye'elimite. Vapnikite has irregular fracture, cleavage and parting were not observed. The calculated density is 5.322 g cm-3, the microhardness is VHN25 = 534 kg mm -2 (mean of seven measurements) corresponding to the hardness of ∼5 on the Mohs scale. The crystal structure of vapnikite Ca 3UO6 differs from that of its synthetic analogue β-Ca3UO6 by having a larger degree of Ca, U disorder. Vapnikite formed at the high-temperature retrograde stage of pyrometamorphism when larnite rocks were altered by fluids/melts of high alkalinity. © 2014 The Mineralogical Society.


Galuskina I.O.,University of Silesia | Vapnik Y.,Ben - Gurion University of the Negev | Lazic B.,University of Bern | Armbruster T.,University of Bern | And 2 more authors.
American Mineralogist | Year: 2014

Harmunite, naturally occurring calcium ferrite CaFe2O 4, was discovered in the Hatrurim Complex of pyrometamorphic larnite rocks close to the Jabel Harmun, the Judean Desert, West Bank, Palestinian Autonomy, Israel. The new mineral occurs in larnite pebbles of the pseudo-conglomerate, the cement of which consists of intensely altered larnite-bearing rocks. Srebrodolskite, magnesioferrite, and harmunite are intergrown forming black porous aggregates to the central part of the pebbles. Larnite, fluorellestadite, ye'elimite, fluormayenite, gehlenite, ternesite, and calciolangbeinite are the main associated minerals. Empirical crystal chemical formula of harmunite from type specimen is as follows Ca1.013(Fe 3 1+957Al0 015Cr3+ 0.011Ti4+ 0.004 Mg0 003)Σ 1 993O4. Calculated density is 4.404 g/cm3, microhardness VHN50 is 655 kg/mm2. The Raman spectrum of harmunite is similar to that of the synthetic analog. Harmunite in hand specimen is black and under reflected plane-polarized light is light gray with red internal reflections. Reflectance data for the COM wavelengths vary from ∼22% (400 nm) to ∼18% (700 nm). The crystal structure of harmunite [Pnma; a = 9.2183(3), b = 3.0175(1), c = 10.6934(4) Å; Z = 4, V = 297.45(2) Å3], analogous to the synthetic counterpart, was refined from X-ray single-crystal data to R1 = 0.0262. The structure of CaFe2O4 consist of two symmetrically independent FeO 6 octahedra connected over common edges, forming double rutile-type 1∞[Fe2O6] chains. Four such double chains are further linked by common oxygen corners creating a tunnel-structure with large trigonal prismatic cavities occupied by Ca along [001]. The strongest diffraction lines are as follows [dhkl, (I)]: 2.6632(100), 2.5244(60), 2.6697(52), 1.8335(40), 2.5225(35), 2.2318(34), 1.8307(27), 1.5098 (19). Crystallization of harmunite takes place in the presence of sulfate melt.


Galuskin E.V.,University of Silesia | Gfeller F.,University of Bern | Armbruster T.,University of Bern | Galuskina I.O.,University of Silesia | And 8 more authors.
European Journal of Mineralogy | Year: 2015

Two new mineral species of the mayenite group, fluormayenite Ca12Al14O32[□4F2] (I43d, a = 11.9894(2) Å, V = 1723.42(5) Å3, Z = 2) and fluorkyuygenite Ca12Al14O32[(H2O)4F2] (I43d, a = 11.966(2) Å, V = 1713.4(1) Å3, Z = 2), are major constituents of larnite pyrometamorphic rocks of the Hatrurim Complex (Mottled Zone) distributed along the Dead Sea rift on the territory of Israel, Palestinian Autonomy and Jordan. Holotype specimens of fluormayenite and fluorkyuygenite were collected at the Jabel Harmun, Judean Mts., Palestinian Autonomy and in the Hatrurim Basin, Negev Desert, Israel, respectively. Mineral associations of holotype fluormayenite and fluorkyuygenite are similar and include larnite, shulamitite, Cr-containing spinel-magnesioferrite series, ye'elimite, fluorapatite-fluorellestadite, periclase, brownmillerite, oldhamite as well as the retrograde phases portlandite, hematite, hillebrandite, afwillite, foshagite, ettringite, katoite and hydrocalumite. Fluormayenite and fluorkyuygenite crystals, usually < 20 μm in size, are colourless, in places with greenish or yellowish tint, the streak is white. Both minerals are transparent with a vitreous lustre; they do not show fluorescence. Fluormayenite and fluorkyuygenite are isotropic and have similar refractive indices: n = 1.612(3) and n = 1.610(3) (589 nm), respectively. The hardness of fluormayenite and fluorkyuygenite is H (Mohs) 51/2-6; VHN load 50 g, 771(38) kg mm-2; and 5-51/2; VHN load 50 g, 712(83) kg m-2, respectively. Both minerals have the microporous tetrahedral framework structure characteristic of the mayenite supergroup. In fluormayenite 1/3 of the structural cages are occupied by fluorine. In fluorkyuygenite, in addition to fluorine and negligible amounts of OH, H2O molecules occupy about 2/3 of the cages. The holotype fluormayenite from Jabel Harmun has the crystal chemical formula (Ca11.951Na0.037)Σ11.987(Al13.675Fe3+ 0.270Mg0.040Si0.009P0.005S6+ 0.013)Σ14.013 O31.503(OH)1.492[□4.581F1.375Cl0.044]Σ6, fluorkyuygenite from the Hatrurim Basin has the composition Ca12.034(Al13.344Fe3+ 0.398 Si0.224)Σ13.966O32[(H2O)3.810F1.894 (OH)0.296]Σ6. Raman spectra of fluormayenite and fluorkyuygenite in the spectral region 200-1000 cm-1 are similar and are characterized by the four strong main bands at about 320 (ν2 AlO4), 520 (ν4 AlO4), 700, 770 (ν1 AlO4) cm-1. In the O-H vibration region fluorkyuygenite shows a broad band between 2600-3500 cm-1 (νH2O). The molecular water is completely released from the fluorkyuygenite structure at about 400°C. Fluorkyuygenite crystallized initially as fluormayenite, which later was altered under influence of water vapour-enriched gases during a combustion process. Fluormayenite has been synthesized and fluorkyuygenite is an analogue of the recently discovered chlorkyuygenite, Ca12Al14O32[(H2O)4Cl2], from the Northern Caucasus, Russia. © 2014 E. Schweizerbart sche Verlagsbuchhandlung.


Sokol E.V.,RAS Institute of Geology and Mineralogy | Gaskova O.L.,Novosibirsk State University | Kokh S.N.,RAS Institute of Geology and Mineralogy | Kozmenko O.A.,RAS Institute of Geology and Mineralogy | And 3 more authors.
American Mineralogist | Year: 2011

Chromatite (CaCrO4, tetragonal) is mainly known from Cr 6+-contaminated soils associated with chromium ore processing residue. This extremely rare mineral was found at the Nabi Musa locality (Judean Desert Israel), in a peculiar rock complex of the Mottled Zone. We have explored the possible mechanisms responsible for leaching Cr6+ from natural rocks, by means of field observations, batch experiments, thermodynamic modeling, and mineralogical analyses of the Nabi Musa rocks (XRPD, EMPA, SEM, FTIR, and optical microscopy). A remarkable feature of the Mottled Zone rocks is a broad occurrence of high- and ultrahigh-temperature combustion metamorphic rocks, with Cr3+ accumulated mainly in opaque minerals such as Fe-spinel, brownmillerite, and perovskite. Another feature of the Mottled Zone sequence is abundant Cr3+ (bentorite and volkonskoite) and Cr 6+ mineralization (Cr6+-bearing ettringite and baryte-hashemite solid solution) in low-temperature hydrothermal veins. Field, mineralogical, and thermodynamic modeling data suggest that Cr was leached from Cr3+-bearing opaque minerals during late hydrothermal alteration of combustion metamorphic rocks by unusual hyperalkaline waters (pH up to 12). The Cr3+ was then oxidized to Cr6+, and subsequently partially immobilized in Cr6+-bearing ettringite. As a consequence of the highway construction across Nabi Musa hill in 2006, the buried veins filled by Cr6+-substituted ettringite were exhumed and exposed to supergene alteration. The ensuing decomposition of Cr6+-bearing ettringite was followed by Cr6+ release into pore waters in rainy seasons, and then by precipitation of chromatite on the evaporation barrier under the hard desert insolation in dry seasons. The chromatite formation has been due to both unique rock and water chemistry of the Mottled Zone sequence and to the arid climate of the Judean Desert.

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