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We have undertaken a study of the rare ammonium uranyl sulphate mineral, ammoniozippeite, from the Jáchymov ore district, Krušné hory Mountains (Czech Republic). It has been found on a few specimens and forms rich crystalline aggregates in thin cracks of supergene altered rocks with uraninite veinlets in association with gypsum. Its radially arranged aggregates are composed by well-developed flattened acicular crystals up to 1 mm in length. Ammoniozippeite is bright yellow and locally even yellow-orange with pale yellow streak and fluoresces yellow, weak or dull under 254 nm and 366 nm UV-radiation, respectively. Ammoniozippeite crystals are transparent to translucent and have an intensive vitrous luster. It is a very brittle and at least one system of perfect cleavage (along {010}) was observed. The quantitative chemical analyses of ammoniozippeite agree well with the proposed ideal composition and correspond to the following empirical formula [(NH4 )1.96K0.11] Σ2.07[(UO2 )2 (SO4 )1.98O2.06]·H2 O (on the basis of 2 U atoms pfu). Ammoniozippeite is orthorhombic, the space group Ccmb, with the unit-cell parameters refined from X-ray powder diffraction data: a 8.7862(13), b 14.1579(19), c 17.162(2) Å and V 2134.8(4) ų . Vibrational (Raman and infrared) spectroscopy documented the presence molecular water, ammonium, uranyl and suphate units in the crystal structure of ammoniozippeite. [ABSTRACT FROM AUTHOR]

Stibioústalečite, Cu12(Sb2Te2)Se13, was approved as a new mineral species from the Ústaleč mine, 15 km west of Horažďovice, SW Bohemia, Czech Republic. It occurs as metallic anhedral grains up to 0.1-0.3 mm in size, dark grey in color, in a calcite gangue. It is directly associated with hakite-(Hg), berzelianite, the not-yet approved phase Cu12(As2Te2)Se13 and uraninite. Stibioústalečite is brittle, with an indistinct cleavage and a conchoidal fracture; the calculated density is 5.676 g/cm3. In reflected light, stibioústalečite is isotropic, and grey in color; internal reflections were not observed. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 33.3; 546: 33.2; 589: 33.1; 650: 33.0. Electron microprobe analysis for holotype material (grain used for single-crystal X-ray study) gave (in wt. % - average of 7 spot analyses): Cu 34.10, Ag 1.22, Fe 0.04, Zn 0.09, Hg 0.33, Sb 9.39, As 0.70, Te 12.41, S 3.76, Se 37.59, total 99.63. On the basis of (As + Sb + Te) = 4 atoms per formula unit (apfu), the empirical formula of stibioústalečite is M(2)(Cu5.75Ag0.25)Σ6 M(1)(Cu5.93Hg0.04Zn0.03Fe0.02)Σ6.02 X(3)(Te2.12Sb1.68As0.20)Σ4(Se10.36S2.55)Σ12.91. The ideal formula is Cu6Cu6(Sb2Te2)Se13, which requires Cu 33.33, Sb 10.64 Te 11.16 Se 44.87, total 100 wt. %. Stibioústalečite is cubic, I4̄ 3m, with unit-cell parameters a = 10.828(4) Å, V = 1269.6(9) Å3, Z = 2. The crystal structure of stibioústalečite was studied by single--crystal X-ray diffraction data and it is isotypic with other members of the tetrahedrite group. The mineral is named after its type locality Ústaleč and its chemical composition, being the (Sb/Te) end-member in the possible ústalečite series. [ABSTRACT FROM AUTHOR]

Uraniferous bitumens found in black shales from the Permian rocks at Vrchlabí in the Krkonoše Piedmont Basin (Czech Republic) were described and characterized petrologically and mineralogically. The Permian sediments originated from weathering products in metasediments and granitoids of the Krkonoše–Jizera and Orlice–Sněžník crystalline complexes. The organic matter contained up to 4.8 wt.% uranium, as uraninite grains. Elements associated with uraninite, such as Pb, Zr, Cu, and As, may have accumulated from epigenetic fluids in layers rich in organic matter during their late diagenesis. The bitumen structures were extremely heterogeneous, a feature attributed to the radiolytic effects of uranium. Amorphous bitumens, alternating with various forms of nodular and corroded bitumen types from multiple generations, were present. Low and highly altered bitumens with weak anisotropy were recognized, together with halo zones, with reflectance up to 4.37%. The halo zones differed in size, brightness, and reflectance, increasing from the edge to the center. Halos often revealed dark rims between uraninite inclusions and clear zones, originating probably as a result of weaker alterations in organic matter due to the presence of other inorganic components. Uranium concentration was the main factor controlling the degree of radiolytic alteration. The studied uraniferous bitumens are an excellent example of multistage formation and diverse evolution during burial and diagenesis. [ABSTRACT FROM AUTHOR]

Kroupaite (IMA 2017-031), ideally KPb0.5[(UO2)8O4(OH)10]·10H2O, is a new uranyl-oxide hydroxylhydrate mineral found underground in the Svornost mine, Jáchymov, Czechia. Electron-probe microanalysis (WDS) provided the empirical formula (K1.28Na0.07)S1.35(Pb0.23Cu0.14Ca0.05Bi0.03Co0.02Al0.01)S0.48 [(UO2)7.90(SO4)0.04O4.04(OH)10.00]·10H2O, on the basis of 40 O atoms apfu. Sheets in the crystal structure of kroupaite adopt the fourmarierite anion topology, and therefore kroupaite belongs to the schoepitefamily of minerals with related structures differing in the interlayer composition and arrangement, and charge of the sheets. Uptake of dangerous radionuclides (90Sr or 135Cs) into the structure of kroupaite and other uranyl-oxide hydroxy-hydrate is evaluated based on crystal-chemical considerations and Voronoi-Dirichlet polyhedra measures. These calculations show the importance of these phases for the safe disposal of nuclear waste. [ABSTRACT FROM AUTHOR]

Uraninite and the supergene minerals from the Červená hydrothermal uranium vein (Jáchymov ore district, Czech Republic) were studied. These supergene minerals represent alteration products of the joint weathering of uraninite and hypogene sulfide minerals, connected to the acid-mine drainage (AMD) systems. The complex geochemistry of the hypogene mineralization provided a unique environment for formation of chemically diverse supergene phases. Among other features, the weathering system is characterized by the high activity of Cu2+ and REE, which control the composition of the resulting supergene minerals: commonly occurring are Cu-dominant uranyl sulfates of the zippeite group (pseudojohannite, Cu-rabejacite), Cu-dominant uranyl silicates (cuprosklodowksite) or Y- and REE-containing uranyl-sulfate mineral sejkoraite-(Y). The high activity of Cu2+ and REE is also reflected by the fact that both elements enter minerals, which are nominally Cu- or REE-free (marécottite, rabejacite, tyuyamunite, and compreignacite). The alteration association was evaluated with regard to the crystal-chemical properties of each mineral using the bond-valence approach, documenting distinct evolutionary trends during weathering. [ABSTRACT FROM AUTHOR]

Sejkoraite-(Y), the triclinic Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., is a new member of the zippeite group from the Cervená vein, Jáchymov (Street Joachimsthal) ore district, Western Bohemia, Czech Republic. It grows on altered surface of relics of primary minerals: uraninite, chalcopyrite, and tennantite, and is associated with pseudojohannite, rabejacite, uranopilite, zippeite, and gypsum. Sejkoraite-(Y) forms crystalline aggregates consisting of yellow-orange to orange crystals, rarely up to 1 mm in diameter. The crystals have a strong vitreous luster and a pale yellow-to-yellow streak. The crystals are very brittle with perfect {100} cleavage and uneven fracture. The Mohs hardness is about 2. The mineral is not fluorescent either in short- or long-wavelength UV radiation. Sejkoraite-(Y) is yellow, with no visible pleochroism, biaxial negative with α' = 1.62(2), β' = 1.662(3), γ' = 1.73(1), 2Vcalc = 79°. The empirical chemical formula (mean of 8 electron microprobe point analyses) was calculated on the basis of 12 (S + U) atoms: Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Sejkoraite-(Y) is triclinic, space group P1̄, a = 14.0743(6), b = 17.4174(7), c = 17.7062(8) Å, α = 75.933(4), β = 128.001(5), γ = 74.419(4)°, V = 2777.00(19) Å , Z = 2, Dcalc = 4.04 g/cm³. The seven strongest reflections in the X-ray powder diffraction pattern are [dobs in Å (I) (hkl)]: 9.28 (100) (100), 4.64 (39) (200), 3.631 (6) (1̄42), 3.451 (13) (1̄44), 3.385 (10) (24̅2), 3.292 (9) (044), 3.904(7) (300), 2.984 (10) (1̄4̄2). The crystal structure of sejkoraite-(Y) has been solved by the charge flipping method from single-crystal X-ray diffraction data and refined to Robs = 0.060 with GOFobs = 2.38, based on 6511 observed reflections. The crystal structure consists of uranyl sulfate sheets of zippeite anion topology, which alternate with an interlayer containing Y3+ (H2O)n polyhedra and uncoordinated H2O groups. Two yttrium atoms are linked to the sheet directly via uranyl oxygen atom, and the remaining one is bonded by hydrogen bonds only. In the Raman and infrared spectrum of sejkoraite-(Y) there are dominating stretching vibrations of SO4 tetrahedra (~1200-1100 cm-1), Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. stretching vibrations (~900-800 cm-1), and O-H stretching (~3500-3200 cm-1) and H-O-H bending modes (~1640 cm-1). The new mineral is named to honor Jiří Sejkora, a Czech mineralogist of the National Museum in Prague. [ABSTRACT FROM AUTHOR]

Schröckingerite was found in the abandoned 5. kvìěten adit of the Vrchoslav hydrothermal fluorite deposit, the Krušné hory Mountains, northern Bohemia, Czech Republic. It forms green-yellow globular to irregular crystalline aggregates with pearly luster up to 3 mm in diameter on the fragments of rocks and walls of adit. Schröckingerite aggregates are formed by small thin tabular crystals up to 0.07 mm with obviously parallel orientation. Rarely in association with schröckingerite there also were bright orange powdery aggregates of natrozippeite observed. The unit-cell parameters of schröckingerite refined from powder X-ray data are: a = 9.6279(9) Å, b = 9.6303(9) Å, c = 14.3868(11) Å, α = 91.360(9)°, β = 92.292(10)°, γ = 120.191(6)° and V= 1150.59(6) ų. In the infrared spectrum of schröckingerite, the bands of (CO3)2-, (SO4)2- and (UO2)2+ groups as well as molecular H2O were identified. The bond-lengths with values of 1.762 Å, 1.778 Å and 1.769 Å depending on the empirical formula used were calculated from the wavenumber of uranyl bands. Schröckingerite was formed as a sub-recent supergene phase in relatively dry environment from the solutions produced by weathering of the primary U phases (uraninite) associated probably with Nb-Ta minerals in granite and rare pyrite and their interaction with calcite and wall rocks. [ABSTRACT FROM AUTHOR]

An interesting mineral assemblage consisting of uraninite, anilite, covellite, clausthalite, chalcopyrite, tetrahedrite and naumannite? accompanied with wulfenite and supergene uranium minerals was identified using electron microprobe and XRD in material collected in dumps of the small abandoned uranium occurrence at Dlažov, western of Klatovy, SW Bohemia (Czech Republic). Uranium mineralization is bound to quartz-carbonate hydrothermal veins penetrating mostly contact metamorphosed sediments of Proterozoic age adjacent to the Klatovy granodiorite. Sulphides and selenides forms a tiny unequal veinlets in quartz gangue accompanied by uraninite. Supergene uranium minerals comprise meta/autunite, meta/torbernite, uranophane, and β-uranophane. [ABSTRACT FROM AUTHOR]

The Jánská vein is one of the important veins of Březové Hory mining district (central Bohemia, Czech Republic). Base metals were mined here since 14th century and uranium ore during late 1950's. Uranium mineralization is younger than most of the base metal mineralization according to macroscopic and microscopic study. Most specimens of uraninite, obtained from archive, contain more or less abundant galena inclusions. Galena of this type is non-radiogenic as indicated by its Pb isotopic composition (ICP-MS). Its origin can be explained by remobilisation of the older base-metal mineralization during the younger, uranium-bearing mineralization event. The amount of radiogenic Pb in uraninite fluctuates from 48 up to 89.8%. The age of theoretical end member of uraninite, calculated statistically from all measured data (for intersection 208Pb/206Pb = 0), is 269.8 ± 20.3 Ma (2σ). The only uraninite grain without galena inclusions yielded an age of 263.2 ± 8.9 Ma by chemical dating using electron microprobe. The calculated age of the uranium mineralization is in agreement with published data for other uranium deposits genetically associated with the Central Bohemian Plutonic Complex. [ABSTRACT FROM AUTHOR]

A comprehensive study of monazite–cheralite–huttonite solid solutions (s.s.) and xenotime from the highly evolved, strongly peraluminous P–F–Li-rich Podlesí granite stock in the Krušné Hory Mts., Czech Republic, indicates that, with the increasing degree of magmatic and high-T early post-magmatic evolution, the content of the cheralite component in monazite increases and the relative dominance of middle rare earth elements (MREE) in xenotime becomes larger. Considering the overall compositional signatures of these two accessory minerals in the late Variscan granites of the Erzgebirge/Krušné Hory Mts., three types of granites can be distinguished: (i) chemically less evolved F-poor S(I)- and A-type granites contain monazite with a smooth, mostly symmetric chondrite-normalized (CN) rare-earth elements (REE) pattern gradually declining from La to Gd; associated xenotime is Y-rich (˃0.8 apfu Y) with a flat MREE–HREE (heavy rare earth elements) pattern; (ii) fractionated A-type granites typically contain La-depleted monazite with Th accommodated as the huttonite component, combined with usually Y-poor (0.4–0.6 apfu Y) xenotime characterized by a smoothly inclining, Yb–Lu-dominant CN-REE pattern; (iii) fractionated peraluminous Li-mica granites host monazite with a flat, asymmetric (kinked at La and Nd) CN-LREE pattern, with associated xenotime distinctly MREE (Gd–Tb–Dy)-dominant. Monazite and xenotime account for the bulk of the REE budgets in all types of granite. In peraluminous S(I)-type granites, which do not bear thorite, almost all Th is accommodated in monazite–cheralite s.s. In contrast, Th budgets in A-type granites are accounted for by monazite–huttonite s.s. together with thorite. The largest portion of U is accommodated in uraninite, if present. [ABSTRACT FROM AUTHOR]

The Bohemian magmatic complex belongs to granitoid plutons of the Central European Variscides. Hydrothermal uranium mineralization evolved in the small uranium deposits Nahošín and Mečichov is associated with N–S shear zones occurring on the SW margin of the Central Bohemian plutonic complex formed by amphibole-bearing biotite granodiorites of the Blatná suite. The purpose of presented study is description of uranium mineralization bounded on brittle shear zones, which is coupled with intense low-temperature hydrothermal alteration of granitic rocks. Uranium mineralization, formed predominantly of coffinite, rare uraninite, and thorite, is accompanied by intense hematitization, albitization, chloritization, and carbonatization of original granitic rocks that could be described as aceites. These alterations are accompanied by the enrichment in U, Ti, Mg, Ca, Na, K, Y, and Zr and depletion in Si, Ba, and Sr. The analyzed coffinite is enriched in Y (up to 3.1 wt % Y2O3). Uraninite is enriched in Th (up to 9.8 wt % ThO2) and thorite is enriched in Zr (up to 5.7 wt % ZrO2). The REE-elements are concentrated in the REE-fluorcarbonate synchysite-(Ce). [ABSTRACT FROM AUTHOR]

A vanadium mineral montroseite was recently found at the little uranium deposit Licomĕřice in the Železné hory Mountains, Czech Republic. This mineral is known from several ore deposits in Czech Massif (Příbram, Rožná) where accompanies uranium ores. At Licomĕřice, montroseite forms black fine-grained aggregates associated with similar uraninite in calcite gangue. Its powder X-ray diffraction data and chemical composition correspond to those given for this mineral phase in the literature. [ABSTRACT FROM AUTHOR]