Sample records for bassetite

  1. Weathering of mine wastes after historical silver mining in the Jachymov ore district (Czech Republic) and migration of uranium

    International Nuclear Information System (INIS)

    Weathering of 450 years old mine wastes after silver mining at Geister vein in the Jachymov ore district (Czech Republic) and migration of uranium were studied. Specific gamma-ray activity of 226Ra, measured by field gamma-ray spectrometry, varies from 38 Bq/kg (3 ppm eU) to 3816 Bq/kg (309 ppm eU) in the observed area. The most active material forms the top layer of the dump. The gamma-ray activity of the top layer is caused mainly by 226Ra. Uranium is leached from upper layer and accumulated in fossil soils beneath. U-micas were studied using X-ray powder diffraction and EDA. The following succession of supergene alteration was found: autunite → meta-autunite → bassetite →- oxidized bassetite. (author)

  2. U6+ phases in the weathering zone of the Bangombe U-deposit: observed and predicted mineralogy

    International Nuclear Information System (INIS)

    The mineralogy of the supergene-weathered Bangombe natural fission reactor (RZB) and surrounding uranium deposit has been analyzed and compared with the thermodynamically predicted minerals based on groundwater compositions. The primary U-minerals are uraninite UO2+x and minor coffinite (U[SiO4].nH2O); sometimes with phosphorous. The U6+ minerals include fourmarierite Pb1-x[(UO2)4O3-2x(OH)4+2x].4(H2O), bassetite (Fe1-x2+Fex3+[(UO2)(PO4)]2(OH)x.8-xH2O); possibly associated with U(HPO4)2.2H2O and/or chernikovite ((H3O)2[(UO2)(PO4)]2.6H2O); torbernite (Cu[(UO2)(PO4)]2.8-12H2O), Ce-francoisite-(Nd) (REE(UO2)3O(OH)(PO4)2.6H2O), and uranopilite ((UO2)6(SO4)O2(OH)6(H2O)6.8H2O). Autunite (Ca[(UO2)(PO4)]2.10-12H2O) has also been reported. Thermodynamic equilibrium modeling was completed using Geochemist's Workbench trademark with an expanded data base and the groundwater composition (-112 mV ≤ Eh ≤ 143 mV; pH = 5.96) at the base of RZB in drill-hole BAX03. The new ΔGf,298.150 data were obtained from the literature or estimated using the polyhedral contribution method. Based on the updated database, Eh-pH diagrams predict that coffinite, U(HPO4)2.H2O and UOF2.H2O are the only stable U4+ phases and that uranopilite, torbernite and bassetite will become stable during oxidative alteration. Except from UOF2.H2O, this is in accord with mineralogical observations. The role of Cu was predicted from log aCu-pH diagrams, which predicts that torbernite is stable at log aCu = 3.98 x 10-14 and pH ≥ 2.2 at Eh = 143 mV in BAX03 groundwaters. At Eh = -112 mV, torbernite is stable at pH > 5.5. Soddyite ((UO2)2SiO4.2H2O) was predicted to form at the expense of coffinite, but soddyite has not been identified at Bangombe. Previous blind prediction modeling, often omitting P and S, had only predicted soddyite and haiweeite (Ca(UO2)2[Si5O12(OH)2].4-5H2O) and hence, failed to predict the U6+ minerals observed at Bangombe. The results stress the importance of SO42- and PO43- resulting from

  3. Phurcalite and others secondary uranium minerals from Perus, Sao Paulo, Brazil

    International Nuclear Information System (INIS)

    Phurcalite has been found filling fractures in the tourmaline-bearing granitic pegmatite of Perus, in the north-west part of Sao Paulo city, Brazil. It forms aggregates of radiating euhedral crystals up to 5 mm in length. The crystals are bright yellow, transparent and display vitreous to adamantine lustre. Its streak is pale yellow. Phurcalite is brittle, with a conchoidal fracture, and non-fluorescent. The crystal structure of phurcalite has been solves by single-crystal x-ray diffraction methods and refined to R = 3.8% using 2065 observed [I > 3σ(I)] reflections. The structure consists of [(U O2)3 O2 (P O4)24n-]n layers, parallel to (010), connected by Ca2+ ions and H2 O. The coordination polyhedra are: for U(1) hexagonal bi pyramid; for U(2) and U(3) pentagonal bi pyramids; for Ca(4) and Ca(5) capped trigonal prism and triangulated dodecahedron, respectively; and for P(6) and P(7) tetrahedra. As a consequence of this work, the molecular formula of phurcalite previously reported as Ca2 (U O2)3 (P O4)2 (OH)4.4 H2 O must be changed to Ca2 (U O2)3 O2 (P O4)2.7 H2 O. Other secondary uranium minerals associated with Perus phurcalite are autunite, torbernite, meta-autunite, meta-torbernite, chernikovite, meta-uranocircite I, phosphuranylite, uranophane-alpha, uranophane-beta, haiweeite, barian week site and perhaps also bassetite, meta-tyuyamunite and meta-haiweeite. Opal, tridymite, cristobalite, secondary quartz, saponite and rhodochrosite occur associated to the uranium minerals. (author)

  4. Uranium bioprecipitation mediated by yeasts utilizing organic phosphorus substrates. (United States)

    Liang, Xinjin; Csetenyi, Laszlo; Gadd, Geoffrey Michael


    In this research, we have demonstrated the ability of several yeast species to mediate U(VI) biomineralization through uranium phosphate biomineral formation when utilizing an organic source of phosphorus (glycerol 2-phosphate disodium salt hydrate (C3H7Na2O6P·xH2O (G2P)) or phytic acid sodium salt hydrate (C6H18O24P6·xNa(+)·yH2O (PyA))) in the presence of soluble UO2(NO3)2. The formation of meta-ankoleite (K2(UO2)2(PO4)2·6(H2O)), chernikovite ((H3O)2(UO2)2(PO4)2·6(H2O)), bassetite (Fe(++)(UO2)2(PO4)2·8(H2O)), and uramphite ((NH4)(UO2)(PO4)·3(H2O)) on cell surfaces was confirmed by X-ray diffraction in yeasts grown in a defined liquid medium amended with uranium and an organic phosphorus source, as well as in yeasts pre-grown in organic phosphorus-containing media and then subsequently exposed to UO2(NO3)2. The resulting minerals depended on the yeast species as well as physico-chemical conditions. The results obtained in this study demonstrate that phosphatase-mediated uranium biomineralization can occur in yeasts supplied with an organic phosphate substrate as sole source of phosphorus. Further understanding of yeast interactions with uranium may be relevant to development of potential treatment methods for uranium waste and utilization of organic phosphate sources and for prediction of microbial impacts on the fate of uranium in the environment. PMID:26846744