Abstract
Pseudojohannite is a hydrated copper(II) uranyl sulfate described from Jáchymov, Northern Bohemia, Czech Republic (type locality). Pseudojohannite also occurs at the Musonoï quarry near Kolwezi, Shaba, Congo, and the La Creusaz prospect, Western Swiss Alps. At all three localities, pseudojohannite formed through the interaction of acid sulfate mine drainage waters with uraninite (Jáchymov and La Creusaz) or uranyl silicates (Musonoï). Pseudojohannite forms moss green, non UV-ß uorescent aggregates consisting of irregularly shaped crystals measuring up to 25 μm in length and displaying an excellent cleavage parallel to (.101). dmeas is 4.31 g/cm3, dcalc 4.38 g/cm3, and the refractive indices are nmin = 1.725 and nmax = 1.740. A high-resolution synchrotron powder diffraction pattern on the material from Musonoï shows that pseudojohannite is triclinic (P1 or P1̅), with a = 10.027(1) Å, b = 10.822(1) Å, c = 13.396(1) Å, α = 87.97(1)°, β = 109.20(1)°, γ = 90.89(1)°, V = 1371.9(5) Å3. The location of the uranium and sulfur atoms in the cell was obtained by direct methods using 1807 reflections extracted from the powder diffractogram. Pseudojohannite contains zippeite-type layers oriented parallel to (.101). The empirical chemical formula calculated for a total of 70 O atoms is Cu6.52U7.85S4.02O70H55.74, leading to the simplified chemical formula Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O. The distance of 9.16 Å between the uranylsulfate sheets in pseudojohannite shows that neighboring layers do not share O atoms with the same CuΦ6 [Φ = (O,OH)] distorted octahedrons, such as in magnesium-zippeite. Rather, it is expected that CuΦ6 forms a layer bound to the zippeite-type layers by hydrogen bonding, as in marécottite, or one apex of the CuΦ6 polyhedron only is shared with a zippeite-type layer, as in synthetic SZIPPMg. The higher number of cations in the interlayer of pseudojohannite (Cu:S = 1.6:1) compared to marécottite (3:4) and SZIPPMg (1:1) indicates that pseudojohannite has a unique interlayer topology. Ab-initio powder structure solution techniques can be used to obtain important structural information on complex micro-crystalline minerals such as those found in the weathering environment. Pseudojohannite represents a new member of the zippeite group of minerals, and further illustrates the structural complexity of zippeite-group minerals containing divalent cations, which have diverse arrangements in the interlayer. Peudojohannite and other divalent zippeites are common, easily overlooked minerals in acid drainage environments around uranium deposits and wastes.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Hourglass sector zoning in metamorphic tourmaline and resultant major and trace-element fractionation
- Occurrence and late re-equilibration of pollucite from the Koktokay no. 3 pegmatite, Altai, northwestern China
- Chemical bonding and electronic structures of the Al2SiO5 polymorphs, andalusite, sillimanite, and kyanite: X-ray photoelectron- and electron energy loss spectroscopy studies
- Application of the simple salt lattice energy approximation to the solubility of minerals
- Quench rate and temperature effects on framework ordering in aluminosilicate melts
- The effect of sodium on the solubilities of metals in silicate melts
- Nanotunnels and pull-aparts: Defects of exsolution lamellae in alkali feldspars
- The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth`s oldest putative microfossils
- Site disorder revealed through Raman spectra from oriented single crystals: A case study on karooite (MgTi2O5)
- Single-crystal diffraction and transmission electron microscopy studies of silicified pyrochlore from Narssârssuk, Julianehaab district, Greenland
- Compressibility of synthetic potassium-rich clinopyroxene: In-situ high-pressure single-crystal X-ray study
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- Relationship among metamorphic grade, vesuvianite ”rod polytypism”, and vesuvianite composition
- Assignment of infrared OH-stretching bands in calcic amphiboles through deuteration and heat treatment
- Direct determination of cation site occupancies in natural ferrite spinels by L2,3 X-ray absorption spectroscopy and X-ray magnetic circular dichroism
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- Fe2+ and Fe3+ quantification by different approaches and fO₂ estimation for Albanian Cr-spinels
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- Chivruaiite, Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]·13-14H2O, a new mineral from hydrothermal veins of Khibiny and Lovozero alkaline massifs
- Pseudojohannite from Jáchymov, Musonoï, and La Creusaz: A new member of the zippeite-group
- Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, a new single-chain silicate
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