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Plasil J.,ASCR Institute of Physics Prague | Fejfarova K.,ASCR Institute of Physics Prague | Hlousek J.,U Rohacovych kasaren 24 | Skoda R.,Masaryk University | And 7 more authors.
Mineralogical Magazine | Year: 2012

Štěpite, tetragonal U(AsO3OH)2(H 2O)4 (IMA 2012-006), is the first natural arsenate of tetravalent uranium. It occurs in the Geschieber vein, Jáchymov ore district, Western Bohemia, Czech Republic, as emerald-green crystalline crusts on altered arsenic. Associated minerals include arsenolite, běhounekite, claudetite, gypsum, kaatialaite, the new mineral vysokýite (IMA 2012-067) and a partially characterized phase with the formula (H3O) 2 +(UO2)2(AsO4) 2·6H2O. Štěpite typically forms tabular crystals with prominent {001} and {010} faces, up to 0.6 mm in size. The crystals have a vitreous lustre and a grey to greenish grey streak. They are brittle with an uneven fracture and a very good cleavage on (001). Their Mohs hardness is about 2. Štěpite is not fluorescent in either short-wave or long-wave ultraviolet light. It is biaxial (-) with refractive indices (at 590 nm) of α = 1.636(2), β = 1.667(3), γ = 1.672(2) and 2Vobs < ∼5°, anomalous greyish to pale yellow interference colours, and no pleochroism. The composition is as follows: 0.12 Na2O, 50.19 UO2, 0.04 SiO4, 0.09 P 2O5, 0.93 As2O5, 1.95 SO 3, 16.41 H2O; total 107.90 wt.%, yielding an empirical formula (based on 12 O a.p.f.u.) of (U1.01Na0.02) Σ1.03[(AsO3OH)1.82(PO3OH) 0.04(SO4)0.13(SiO4) 0.01]Σ2.00·4H2O. Štěpite is tetragonal, crystallizing in space group I4 1/acd, with a = 10.9894(1), c = 32.9109(6) Å, V = 3974.5(1) Å, Z = 16 and Dcalc = 3.90 g cm-3. The six strongest peaks in the X-ray powder-diffraction pattern [dobs in Å (I) (hkl)] are as follows: 8.190(100)(004), 7.008(43)(112), 5.475(18)(200), 4.111(16)(008), 3.395(20)(312,217), 2.1543(25)(419). The crystal structure of štěpite has been solved from single-crystal X-ray diffraction data by the charge-flipping method and refined to R1 = 0.0353 based on 1434 unique observed reflections, and to wR2 = 0.1488 for all 1523 unique reflections. The crystal structure of štěpite consists of sheets perpendicular to [001], made up of eight-coordinate uranium atoms and hydroxyarsenate 'tetrahedra'. The ligands surrounding the uranium atom consist of six oxygen atoms which belong to the hydroxyarsenate groups and two oxygen atoms which belong to interlayer H2O molecules. Each UO8 polyhedron is connected to five other U polyhedra via six AsO3OH groups. Adjacent electroneutral sheets, of composition [U4+(AsO 3OH)2 2-], are linked by hydrogen bonds involving H2O molecules in the interlayers and OH groups in the sheets. The new mineral is named in honour of Josef Štěp (1863 - 1926), a Czech mining engineer and 'father' of the world's first radioactive spa at Jáchymov. © 2013 The Mineralogical Society. Source

Skala R.,Academy of Sciences of the Czech Republic | Ondrus P.,Biskupsky dvur 2 | Veselovsky F.,Czech Geological Survey | Cisarova I.,Charles University | Hlousek J.,Komenskeho 821
Mineralogy and Petrology | Year: 2011

The new mineral agricolaite, a potassium uranyl carbonate with ideal formula K4(UO2)(CO3)3, occurs in vugs of ankerite gangue in gneisses in the abandoned Giftkiesstollen adit at Jáchymov, Czech Republic. The name is after Georgius Agricola (1494-1555), German scholar and scientist. Agricolaite occurs as isolated equant irregular translucent grains to 0.3 mm with yellow color, pale yellow streak, and vitreous luster. It is brittle with uneven fracture and displays neither cleavage nor parting. Agricolaite is non-fluorescent. Mohs hardness is ~4. It is associated with aragonite, brochantite, posnjakite, malachite, rutherfordine, and "pseudo-voglite". Experimental density is higher than 3.3 g. cm-3, Dcalc is 3.531 g. cm-3. The mineral is monoclinic, space group C2/c, with a 10.2380(2), b 9.1930(2), c 12.2110(3) Å, β 95.108(2)°, V 1144.71(4) Å3, Z = 4. The strongest lines in the powder X-ray diffraction pattern are d(I)(hkl): 6.061(55)(002), 5.087(57)(200), 3.740(100)(202), 3.393(43)(113), 2.281(52)(402). Average composition based on ten electron microprobe analyses corresponds to (in wt.%) UO3 48.53, K2O 31.49, CO2(calc) 22.04 which gives the empirical formula K3.98(UO2)1.01(CO3)3.00. The crystal structure was solved from single-crystal X-ray diffraction data and refined to R1 = 0.0184 on the basis of the 1,308 unique reflections with Fo > 4σFo. The structure of agricolaite is identical to that of synthetic K4(UO2)(CO3)3 and consists of separate UO2(CO3)3 groups organized into layers parallel to (100) and two crystallographically non-equivalent sites occupied by K+ cations. Both the mineral and its name were approved by the IMA-CNMNC. © 2011 Springer-Verlag. Source

Sejkora J.,National Museum | Ondrus P.,Biskupsky dvur 2 | Novak M.,Masaryk University
Neues Jahrbuch fur Mineralogie, Abhandlungen | Year: 2010

Veselovskýite, (Zn,Cu,Co)Cu4(AsO4) 2(AsO3OH)2 · 9H2O, is a new supergene mineral from the Geister vein, Mine Rovnost at the Jáchymov ore district (St. Joachimsthal), Czech Republic, commonly associated with strashimirite and blue amorphous Cu arsenate. It forms aggregates, up to 8 × 5 × 1 mm in size, consisting of lath-like to thin-tabular crystals, up to 1 mm long, commonly forming complicated intergrowths, no twinning was observed. Veselovskýite is translucent (aggregates) to transparent (crystals), colourless to greyish white (with a slight greenish tint). It has a greyish white streak with a greenish tint, a vitreous luster, does not fluoresce under both short- and long-wave ultraviolet light. Cleavage on {001} is perfect, Mohs hardness is ∼2-3, and veselovskýite is very brittle with an irregular fracture and calculated density 3.28 g/cm 3. Veselovskýite is biaxial positive, the indices of refraction are nx-1.645(3), ny 1.68(1), nz. ∼1.72, 2V(calc) approximative 88°, it is strongly pleochroic (nx = greenish, ny = pale green, nz = green), and the optical orientation is as follows: nx- versus elongation (c) = 15(1)°. Veselovskýite is triclinic, space group P-1, a 6.4022(4), b 8.0118(4), c 10.3665(4) Å, α 85.491(3)°, β 79.377(4)°, γy 84.704(5)°, V519.34(4) Å3, Z=1, a:b:c = 0.7991:1:1.2939. The eight strongest lines in the X-ray powder diffraction pattern are as follows: d (Å), I, (hkl): 10.185, 100 (001), 7.974, 12 (010), 3.987, 13 (020), 3.637, 15 (0-21), 3.395, 37 (003), 3.238, 15 (022), 2.910, 12 (202), 2.668, 16 (023). The chemical analyses by electron microprobe yielded MgO 0.05. CaO 0.04, MnO 0.22, NiO 0.30, CoO 0.96, CuO 32.98, ZnO 3.39, Al2O3 0.24, P2O5, As 2O5 43.16, H2O 17.90, total ( 100.00) wt.%. The resulting empirical formula on the basis of 25 (O, OH, H2O) anions is (Zn0 43Cu0 24Co0 13,Al0 05Ni 0 04Mn0 03Mg0 01Ca0 01) Σ0 94Cu4 00 [(AsO4) 1 92(PO4)0 11(AsO3OH) 1 92] · 9.20H2O. The ideal end-member formula ZnCu4[(AsO4)2(AsO3OH)2] · 9H2O requires ZnO 7.83, CuO 30.61, As2O 5 44.22, H2O 17.34, total 100.00 wt.%. Veselovskýite is isostructural with lindackerite and represents Zn-dominant analogue of lindackerite and pradetite. The name veselovskýite is in honor of František Veselovský (*1948), an outstanding Czech mineralogist, who described several new minerals from the Jáchymov ore district. © 2010 E. Schwelzerbart'sche Verlagsbuchhandlung, Stuttgart, Germany. 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

Ondrus P.,Biskupsky dvur 2 | Skala R.,Academy of Sciences of the Czech Republic | Plasil J.,ASCR Institute of Physics Prague | Sejkora J.,National Museum | And 11 more authors.
Mineralogical Magazine | Year: 2013

Švenekite (IMA 99-007), Ca[AsO2(OH)2] 2, is a rare supergene arsenate mineral occurring in the Geschieber vein, Jáchymov ore district, Western Bohemia, Czech Republic. It grows directly on the granite rocks and occurs isolated from other arsenate minerals otherwise common in Jáchymov. Švenekite usually forms clear transparent coatings composed of indistinct radiating to rosette-shaped aggregates up to 3 mm across. They are composed of thin lens-or bladed-shaped crystals, usually 100-150 μm long. Švenekite is transparent to translucent and has a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. Cleavage is very good on {010}. The Mohs hardness is ∼2. Švenekite is biaxial, non-pleochroic. The refractive indices are α' = 1.602(2), γ' = 1.658(2). The empirical formula of švenekite (based on As + P + S = 2 a.p.f.u., an average of 10 spot analyses) is (Ca1.00Mg0.01)Σ1.01[AsO 2(OH)2]1.96[PO2(OH) 2]0.03(SO4)0.01. The simplified formula is Ca[AsO2(OH)2]2 and requires CaO 17.42, As2O571.39, H2O 11.19, total 100.00 wt.%. Raman and infrared spectroscopy exhibit dominance of O-H vibrations and vibration modes of distorted tetrahedral AsO2(OH)2 units. Švenekite is triclinic, space group P1, with a = 8.5606(5), b = 7.6926(6), c = 5.7206(4) Å, a = 92.605(6), b = 109.9002(6), g = 109.9017(6)°, and V = 327.48(4) Å3, Z = 2, D calc = 3.26 g·cm-3. The a:b:c ratio is 0.7436:1:1.1082 (for single-crystal data). The six strongest diffraction peaks in the X-ray powder diffraction pattern are [d (Å)/I(%)/(hkl)]: 3.968(33)(210); 3.766(35)(211); 3.697(49)(101); 3.554(100)(020); 3.259(33)(220); 3.097(49)(121). The crystal structure of švenekite was refined from single-crystal X-ray diffraction data to R 1 = 0.0250 based on 1309 unique observed, and to wR 2 = 0.0588, for all 1588 unique reflections (with GOFall = 1.20). The structure of švenekite consists of sheets of corner-sharing CaO8 polyhedra and AsO 2 OH2 groups, stacked parallel to (001). Adjacent sheets are linked by hydrogen bonds. The švenekite structure possesses very short symmetrical hydrogen bonds (with the D-H lengths ∼1.22 Å). The mineral is named to honour Jaroslav Švenek, the former curator of the mineralogical collection of the National Museum in Prague, Czech Republic. © 2013 Mineralogical Society. Source

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