Search

An interesting Se and Cu mineralization has been found in the dumps of the abandoned uranium occurrence Bílá Voda near Javorník, Rychlebské hory Mountains, Czech Republic. Uraninite forms abundant aggregates up to 1 - 2 mm in size formed by spherical to hemi-spherical aggregates up to 50 - 100 μm across. Its chemical composition corresponds to the empirical formula [(U0.57Si0.08)Σ0.65(REE+Y)0.09(Ca0.15 Cu0.05Pb0.03Fe0.02)Σ0.25]O1.68. Mineral phase close to coffinite was observed in association with uraninite and Cu minerals as collomorphic aggregates up to 1 mm in size. Beside dominant U (27 - 37 at. %) it contains a very unusual contents of Cu (18 - 25 at. %) and ΣREE+Y (11 - 13 at. %); Si varies in the range 12 - 29 at. %. Chalcopyrite forms crystalline grains up to 1 mm across, aggregates composed by prismatic crystals up to 100 μm in length and altered relics up to 100 μm in association with covelline, bornite, unnamed Cu9Fe7S16, uraninite and Cu-rich coffinite. Its chemical composition can be expressed by the empirical formula Cu1.00Fe0.98(S2.00Se0.02)Σ2.02. Rammelsbergite was found as crystalline aggregates up to 100 μm. For its chemical composition is characteristic NiCo-1 substitution with Co contents in the range 0.18 - 0.44 apfu. Löllingite and safflorite were observed more rarely as grains up to 50 μm in association with rammelsbergite and nickeline. For löllingite, the FeNi-1 substitution with contents of Ni in the range 0.06 až 0.40 apfu is dominant. The chemical composition of safflorite varies especially in Co/Ni/Fe ratios. Nickeline occurs only rarely as aggregates up to 50 µm across in association with löllingite group minerals and uraninite. Its chemical composition corresponds to the empirical formula (Ni0.94Co0.03Fe0.01Cu0.01)Σ0.99 (As0.98S0.04)Σ1.02. Silver forms irregular grains up to 30 μm in size in carbonate gangue in association with Ni-Co-Fe arsenides, its empirical formula is (Ag0.99Hg0.01)Σ1.00. Clausthalite occurs as abundant inclusions up to 15 - 20 μm across in bornite, anomalous bornite, digenite, djurleite and covelline. Its chemical composition can be expressed by the empirical formula (Pb0.98Fe0.01Cu0.01)Σ1.00(Se0.9S0.04)Σ1.00. Naumannite was found only rarely as irregular grains and aggregates up to 20 μm in size in association with clausthalite and coffinite. Its empirical formula is (Ag1.97Cu0.03Fe0.01)Σ2.01(Se0.98S0.02)Σ1.00. Bornite forms aggregates up to 500 µm across with abundant tiny clausthalite inclusion; its aggregates are replaced by later digenite and djurleite. Bornite was also observed as pseudomorphoses after chalcopyrite up to 100 µm in length. Its chemical composition corresponds to the empirical formula Cu4.83Fe0.99(S3.95Se0.05)Σ4.00. Chemically anomalous bornite was found as aggregates up to 200 µm in size partly replaced by later covellite and unnamed Cu9Fe7S16. Its empirical formula Cu3.92Fe0.97(S3.98 Se0.02)Σ4.00 is close to ideal composition Cu4FeS4. Digenite occurs as lath-like aggregates up to 100 μm in length strongly altered by later djurleite. Aggregates of digenite and djurleite partly replaced earlier bornite. The chemical composition of digenite can be expressed by the empirical formula (Cu8.98Fe0.02Pb0.01)Σ9.01(S4.90Se0.09)Σ4.99. Djurleite forms aggregates up to 200 μm across with abundant relics of earlier digenite. Its chemical composition corresponds to the empirical formula (Cu30.68Fe0.08Pb0.01)Σ30.77(S15.96S0.27)Σ16.23. Covellite was found in association with uraninite and coffinite as abundant aggregates up to 300 μm in size replacing earlier chalcopyrite and chemically anomalous bornite. Its empirical formula is (Cu1.04Fe0.01)Σ1.05(S0.94Se0.01)Σ0.95. Unnamed Cu sulfide with chemical composition close to Cu9Fe7S16 was observed as elongated or lens-shape crystals up to 20 μm in length in aggregates of earlier covellite and anomalous bornite in association with uraninite and covellite. It also forms elongated crystals and aggregates up to 40 μm in size replacing earlier chemically anomalous bornite. Its chemical composition can be to express by an ideal formula Cu9-xFe7+xS16 (x ±0.5) and by empirical formula Cu9.03(Fe6.99Pb0.02)Σ7.01(S15.89Se0.07)Σ15.96. [ABSTRACT FROM AUTHOR]

Unusual rich vanadium-uranium mineralization in hydrothermal calcite veins was found at large active quarry Prachovice located about 20 km SW from Pardubice, eastern Bohemia, Czech Republic. Primary minerals: montroseite, melanovanadite, new Ca-Fe-V phase, uraninite and clausthalite are intensely altered to supergene mineral phases: sherwoodite, tyuamunite, rossite, metarossite and pascoite. Montroseite occurs as abundant black hemispherical aggregates up to 25 mm in size and crusts in calcite gangue formed by long tabular to acicular crystals up to 2 mm in length. Melanovanadite was found only rarely as black acicular crystals up to 7 mm in length formed radial aggegates with diameter up to 15 mm. New Ca-Fe-V phase forms very rare black (with bluish tint) well-formed brittle isometric crystals up to 0.7 mm in association with melanovanadite and tyuamunite. Uraninite forms abundant microscopic (up to 50 - 80 μm) grains in montroseite or calcite gangue. Clausthalite was found as very rare microscopis (25 µm) grains in association with uraninite and montroseite. Pascoite occurs as transparent to transluncent brown to orange red crystals up to 1 mm in size and yellow-orange crusts at area about some cm2. Rossite was found as transparent to translucent colourless to white (some with green or blue tint) isometric to tabular crystals up to 0.2 mm in size or white (some with green tint) crystalline crusts at area about 1 x 3 cm. Metarossite formed white to grey fine crystalline crusts (at area up to 3 x 3 cm) on calcite gangue; it was also found as dehydratation product of rossite. Sherwoodite occurs as abundant powder to massive aggregates up to 2 x 10 x 10 cm formed as alteration product of montroseite aggregates. Its colour varies from light green, yellow-green, blue-green to brown-green or dark green. Tyuamunite was found as yellow to greenish yellow tabular crystals up to 1 mm in size and their rich radial aggregates on calcite or montroseite. The powder X-ray diffraction data, refined unit-cell parameters and results of quantitative chemical study of described mineral phases are given in the paper. [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]

Uranium deposit located near the Nahošín village, 10 km SW of Blatná (southwestern Bohemia, Czech Republic) was one of the last (1978 - 1989) explored uranium deposits in the Czech Republic. The deposit Nahošín is situated in the Chanovice part of Central Bohemian Plutonic Complex represented here by the Blatná type of granodiorite. It belongs to metasomatic uranium deposit developed in granitoids. The metasomatic uranium mineralization in granitoids is bound to strongly hydrothermally altered zone (1 to 5 m wide), represented by disseminated coffinite I in association with pyrite, calcite and sporadic galena and clausthalite. The altered granodiorite is reddish in colour, shows indications of leached quartz and the formation of hematite, chlorite, Ti - minerals, albite, K-feldspar and calcite.The increased porosity of intensively altered granodiorite is a characteristic feature. The significant extent of younger (regenarated) contrast vein uranium mineralization was also found here. The vein uranium mineralization occurred at crushed and brecciated zones of hydrothermally altered granitoide. It is represented by uraninite (usually partly replaced by coffinite II) in calcite gangue in association with pyrite and minerals of the galena - clausthalite solid solution. The δ13C and δ18O data of hydrothermal calcite associated with uraninite and coffinite of the younger vein mineralization indicate low temperature of deposition (<150 °C) and a presence of relatively shallow circulating fluids of meteoric provenance. Carbon was most probably derived from more sources, with participation of exogenous carbon during the youngest mineralization stages. Both types uranium mineralization at the Nahošín ore deposit are of late Variscan age probably. [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]