Time filter

Source Type

Prague, Czech Republic

Sejkora J.,National Museum | Plasil J.,University of Bern | Cisarova I.,Charles University | Skoda R.,Masaryk University | And 3 more authors.
Journal of Geosciences | Year: 2011

Rich supergene mineral association with prevalence of Pb was found in a shallow gallery of the Rovnost mine, the Jáchymov (St. Joachimsthal) ore district, western Bohemia (Czech Republic). Mimetite occurs as colourless transparent flexible fibres up to 1 mm in length and up to 10 μm in diameter. The fibres form greyish white aggregates (up to 1 cm2 in area) grown on the surface of gangue strongly affected by supergene alteration. The results of the single crystal X-ray diffraction study of mimetite with R1 = 0.0381 are fully consistent with data reported previously for this mineral phase. According to electron microprobe study, interesting are namely elevated contents of SiO4 (up to 0.16 apfu). Among the supergene minerals, cerussite, anglesite, wulfenite, philipsbornite-segnitite minerals, pyromorphite and metazeunerite were determined based on powder X-ray diffraction and electron microprobe analyses. The presence of U (~ 4 wt. % UO3) and As (up to 4 wt. % As2O5) in wulfenite is particularly noteworthy. Characteristic of the studied mineral association are elevated and omnipresent contents of F-. This mineral assemblage is considered to be a result of a long-term in-situ weathering in near-surface conditions. Source

Sejkora J.,National Museum | Plasil J.,National Museum | Plasil J.,Masaryk University | Ondrus P.,Biskupsky dvur 2 | And 3 more authors.
Canadian Mineralogist | Year: 2010

Slavkovite, Cu13(AsO4)6(AsO 3OH)4· 23H2O, is a newly discovered supergene mineral from the Geschieber vein, Svornost mine at the Jáchymov (St. Joachimsthal) ore district, Czech Republic, commonly associated with lavendulan, geminite, lindackerite and ondrušite. It forms coatings of pale green rosettes up to 1 mm across or individual spherical aggregates up to 5 mm across. Individual acicular to lath-like crystals are up to 1 mm long and 0.05 mm thick, and are colorless with a greenish tint. Slavkovite is pale green, translucent (aggregates) to colorless with a greenish tint, transparent (crystals). It has a white streak and a vitreous luster, and does not fluoresce under both short- and long-wave ultraviolet light. The cleavage on {011} is perfect, and on {010}, it is good. The Mohs hardness is ∼3.5-4; slavkovite is very brittle, with an irregular fracture. Its measured density, 3.05(1) g/cm3, is identical to the calculated one. Slavkovite is biaxial positive; the indices of refraction are α1.591(2), β' 1.620(2), γ' 1.701(2), and the 2V (cale.) is approximately 64°. It is moderately pleochroic (X light gray to colorless, Y very light greenish gray, Z light green). Slavkovite is triclinic, space group P1̄, a 6.408(3), b 14.491(5), c 16.505(8) Å, α 102.87(3), β 101.32(5), γ 97.13(3)°, V 1442(1) Å3, Z=1, a:b:c = 0.4422:1:1.1390. The strongest eight lines in the X-ray powderdiffraction pattern [d in Å(I)(hkl)]are as follows: 15.70(3)(001), 11.98(100)(01̄1), 6.992(3)(02̄1, 020), 5.992(6)(02̄2), 3.448(5) (040), 2.967(5)(03̄5), 2.4069(4)(15̄4), 2.4002(4)(115, 1̄35, 046, 062). The chemical analyses made with an electron microprobe yielded FeO 0.12, CuO 39.93, Al2O3 0.13, As2O5 44.71, H2O 17.31, total 102.20 wt.%. The resulting empirical formula on the basis of 63(O, OH, H2O) anions is (Cu 12.96Al0.07Fe0.04)Σ 13.07(AsO4)6.11 (AsO3OH) 3.93·22.83H2O. The ideal end-member formula, Cu13(AsO4)6(AsO3OH) 4·23 H2O, requires CuO 39.26, As2O 5 43.36, H2O 17.10, total 100.00 wt. %. The crystal structure of slavkovite has been solved by direct method and refined to a final Robs of 4.37% on the basis of 6613 observed reflections collected on a single-crystal diffractometer with MoKα X-radiation. The crystal structure is based upon sheets consisting of copper polyhedra linked by arsenate and hydrogen arsenate tetrahedra. The sheets are linked by bridging Cu6-Φ polyhedra. In the asymmetric unit of the slavkovite unit-cell, seven symmetrically independent Cu2+ atoms, five As5+ atoms and 34 O atoms were found. Two of the oxygen atoms belong to OH- groups and fourteen to H2O molecules. Slavkovite possesses a unique crystal structure that has not been found in any mineral or synthetic compound before. It was named after its first occurrence in the Krásno Sn-W ore district, near Horní Slavkov, Czech Republic. Selected data for slavkovite from this locality are also given. Source

Sejkora J.,National Museum | Plasil J.,National Museum | Plasil J.,Masaryk University | Veselovsky F.,Czech Geological Survey | And 2 more authors.
Canadian Mineralogist | Year: 2011

Ondrušite, CaCu4(AsO4)2(AsO 3OH)2·10H2O, is a new supergene mineral species from the Geister vein (Rovnost mine) and the Geschieber vein (Svornost mine), at the Jáchymov (St. Joachimsthal) ore district, Czech Republic. It is commonly associated with lindackerite, geminite, lavendulan, slavkovite, strashimirite, olivenite, picropharmacolite and köttigite. It forms white, whitish green, grey-green or apple-green crystalline crusts or aggregates composed of fine platy or lath-shaped translucent crystals up to 2 mm in size, on fissures of partly weathered mineralized quartz veins. It has a white to greyish white streak with a greenish tint, and a vitreous luster; it does not fluoresce under both short-and long-wave ultraviolet light. Cleavage on {001} is perfect, the Mohs hardness is ∼2-3, and the mineral is very brittle with an irregular fracture. The measured density, 3.26 g/cm3 (affected by a lavendulan admixture), is slightly higher than a calculated one of 3.12 g/cm3. Ondrušite is biaxial positive; the indices of refraction are α' 1.640(2) and γ' 1.708(2), and it is strongly pleochroic, from colorless to light yellowish green. Ondrušite is triclinic, space group P1̄, a 6.432(1), b 7.986(1), c 10.827(1) Å, α 85.75(1), β 81.25(1), γ 85.04(1)°, V 546.6(1) Å3, Z = 1, a.b.c = 0.8054:1:1.3557. The strongest eight lines in the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are: 10.671(100)(001), 3.970(10)(020), 3.648(11)(021̄), 3.560(18)(003), 3.286(10)(022), 3.173(13)(013̄, 200,201), 2.922(10)(201̄,202) and 2.736(10) (023). The chemical analyses by electron microprobe and the thermal analysis for H2O yielded MgO 0.42, CaO 5.27, NiO 0.03, CoO 0.08. CuO 29.90, PbO 0.16, P2O5 0.33, As2O5 44.92, H2O 19.40, for a total of 100.51 wt.%. The resulting empirical formula, calculated on the basis of 26 (O, OH, H2O) anions, is (Ca0.96Co0.01Pb0.01)Σ0.98 (Cu3.84Mg0 11)Σ3.95 [(AsO 4)1.73(PO4)0.05] Σ1 78 (AsO3OH)2.26·9.86H 2O. The ideal end-member formula, CaCu4(AsO 4)2(AsO3OH)2·10H 2O, requires CaO 5.43, CuO 30.83, As2O5 44.53, H2O 19.20, total 100.00 wt.%. The crystal structure of ondrušite was solved by direct method and refined to a R1 index of 9.80% based on all 2888 reflections collected on a single-crystal diffractometer with MoKα X-radiation. The crystal structure consists of CUO6-ASO4-ASO3OH chains two polyhedra thick that form sheets connected through the bridging CaO6 octahedra. In the sheet-to-sheet bonding, CaO6 octahedra and ASO4 groups are involved, whereas the AsO3OH groups bond the CuO6 polyhedra only. One other H2O group is located between the sheets. OndruSite represents the Ca-Cu-dominant member of the ondrušite - geigerite - chudobaite subgroup of the lindackerite group. Source

Plasil J.,ASCR Institute of Physics Prague | Hlousek J.,U Rohacovych kasaren 24 | Skoda R.,Masaryk University | Nova'K M.,Masaryk University | And 4 more authors.
Mineralogical Magazine | Year: 2013

Vysokýite, U4+[(AsO2(OH)2] 4(H2O)4 (IMA 2012-067), was found growing on an altered surface of massive native As in the Geschieber vein, Jáchymov ore district, Western Bohemia, Czech Republic. The new mineral was found in association with běhounekite, štěpite, kaatialaite, arsenolite, claudetite and gypsum. It forms extremely fibrous light-green crystals up to 8 mm long. Crystals have an alabaster lustre and a greenish-white to greyish streak. Vysokýite is brittle with uneven fracture and perfect cleavage along (100) and (001); the Mohs hardness is ∼2. A density of 3.393 g/cm3 was calculated using the empirical formula and unit-cell parameters obtained from a single-crystal diffraction experiment. Vysokýite is non-fluorescent under short or long wavelength UV radiation. It is colourless under the microscope, measured refractive indices are α' = 1.617(3), γ' = 1.654(3); the estimated optical orientation is α' ∼X, γ' ∼Z. The average of five spot wavelength dispersive spectroscopy (WDS) analyses is 29.44 UO2, 1.03 SiO2, 48.95 As2O5, 0.12 SO3, 15.88 H2O (calc.), total 95.42 wt.%. The empirical formula of vysokýite (based on 20 O a.p.f.u.) is U1.00[AsO2(OH)2] 3.90(SiO4)0.16 (SO4)0.014H 2O. The As-O-H and O-H vibrations dominate in the Raman spectrum. Vysokýite is triclinic, space group P1, with a = 10.749(2), b = 5.044(3), c = 19.1778(7) Å, α = 89.872(15) , β = 121.534(15) , γ = 76.508(15) , and V = 852.1(6) Å3, Z = 2 and D calc = 3.34 gcm-3. The strongest diffraction peaks in the X-ray powder diffraction pattern are [d obs in Å (I rel.)(hkl)]: 8.872(100)(100), 8.067(50)(002), 6.399(7)(103), 4.773(6)(104), 3.411(10)(302), 3.197(18)(313). The crystal structure of vysokýite was solved from single-crystal X-ray diffraction data by the charge-flipping method and refined to R 1 = 0.0595 based on 2718 unique observed reflection, and to wR 2 = 0.1160 for all 4173 unique reflections. The structure of vysokýite consists of UO8 square antiprisms sharing all of their vertices with 8 As-tetrahedra to form infinite chains parallel to [010]. These chains are linked by hydrogen bonds involving terminal (OH) groups of the double-protonated As-tetrahedra and molecules of H2O located between the chains. The new mineral is named in honour of Arnošt Vysoký (1823-1872), the former chief of the Jáchymov mines and smelters, chemist and metallurgist. © 2013 Mineralogical Society. Source

Plasil J.,National Museum | Sejkora J.,National Museum | Cejka J.,National Museum | Novak M.,Masaryk University | And 7 more authors.
Canadian Mineralogist | Year: 2010

Metarauchite, a new mineral species of the autunite group, ideally Ni(UO2)2(ASO4)2(AsO 4)2,is triclinic, space group PĪ, a 7.194(4), b 9.713(5), c 13.201(9) Å, α 75.79(3), β 83.92(5), γ 81.59(4)̊, V 882.2(9) Å3, Z = 2, Dcafc = 3.81 g·cnr-3. It forms crystalline aggregates consisting of yellow to light greenish yellow, translucent to transparent tabular crystals with a vitreous luster, exceptionally up to 0.8 mm in size. They have grown on a surface of altered primary mineral phases: uraninite, arsenopyrite, and nickelskutterudite. Metarauchite is very brittle, with a perfect (011) cleavage and an uneven fracture. The Mohs hardness is about 2. The mineral is not fluorescent either in short- and long-wavelength UV radiation. Metarauchite is biaxial negative, α 1.625(3), β ≈ γ 1.649; the calculated 2Vis 52° with a β of 1.646 and a γ of 1.651, and it is 23° with a β of 1.649 and a γ of 1.650. Metarauchite is not pleochroic. Results of a chemical analysis of the holotype sample, normalized to a total of 100 wt.%, yielded: NiO 6.05, CoO 0.91, MgO 0.09, UO3 56.72, AS 2O5 21.31, P2O5 0.22, S1O 2 0.09, H2O 14.61 (from thermal analysis), with a total of 100 wt.% giving the empirical formula (Ni0.82Co 0.12Mg0.02)Σ0.96(UO2) 2.01 [(AsO4)1.88(PO4)0.03 (SiO4)0.02]Σ1.93·8.21H 20 (on the basis of 20 O.OH atoms). According to the thermal analysis, metarauchite dehydrates in several steps, with a total weight loss of 14.61 wt.%, which corresponds to 8.21 H2O. The infrared spectrum of metarauchite was studied and complemented with its Raman spectrum. Stretching and bending vibrations of the (UO2)2+, (AsQ 4)3- and H2O units were tentatively assigned. Furthermore, U-O bond lengths in uranyl and O-H⋯O hydrogen-bond lengths were inferred from the spectra. Metarauchite occurs at the Schweitzer vein, in the Jáchymov (St. Joachimsthal) ore district, Czech Republic (type locality), in association with metazeunerite, erythrite and gypsum. Selected data for metarauchite from Schneeberg, Germany, associated with Ni-rich metanováčekite and metazeunerite also are given. Source

Discover hidden collaborations