Běhounekite, U(SO4)2(H2O)4, from Jáchymov (St Joachimsthal), Czech Republic: the first natural U4+ sulphate.

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Authors

PLÁŠIL Jakub FEJFAROVÁ Karla NOVÁK Milan DUŠEK Michal ŠKODA Radek HLOUŠEK Jan ČEJKA Jiří MAJZLAN Juraj SEJKORA Jiří MACHOVIČ Vladimír TALLA Dominik

Year of publication 2011
Type Article in Periodical
Magazine / Source Mineralogical Magazine
MU Faculty or unit

Faculty of Science

Citation
Doi http://dx.doi.org/10.1180/minmag.2011.075.6.2739
Field Solid matter physics and magnetism
Keywords uranium minerals; X-ray diffraction; crystal structure; Jana2006
Description Behounekite, orthorhombic U(SO4)2(H2O)4, is the first natural sulphate of U4+. It was found in the Geschieber vein, Jachymov (St Joachimsthal) ore district, Western Bohemia, Czech Republic, crystallized on the altered surface of arsenic. The crystals have a strong vitreous lustre and a grey to greenish grey streak. They are brittle with an uneven fracture and have very good cleavage along {100}. The Mohs hardness is about 2. The empirical formula of behounekite is (U0.99Y0.03)1.02(SO4)1.97(H2O)4. The simplified formula is U(SO4)2(H2O)4. Behounekite is orthorhombic, space group Pnma; the crystal structure consists of layers built up from [8]-coordinate uranium atoms and sulphate tetrahedra. The eight ligands include four oxygen atoms from the sulphate groups and four oxygen atoms from the H2O molecules. Each uranium coordination polyhedron is connected via sulphate tetrahedra with other uranium polyhedra and through hydrogen bonds to the apices of sulphate tetrahedra. Behounekite, orthorhombic U(SO4)2(H2O)4, is the first natural sulphate of U4+. It was found in the Geschieber vein, Jachymov (St Joachimsthal) ore district, Western Bohemia, Czech Republic, crystallized on the altered surface of arsenic. The crystals have a strong vitreous lustre and a grey to greenish grey streak. They are brittle with an uneven fracture and have very good cleavage along {100}. The Mohs hardness is about 2. The empirical formula of behounekite is (U0.99Y0.03)1.02(SO4)1.97(H2O)4. The simplified formula is U(SO4)2(H2O)4. Behounekite is orthorhombic, space group Pnma; the crystal structure consists of layers built up from [8]-coordinate uranium atoms and sulphate tetrahedra. The eight ligands include four oxygen atoms from the sulphate groups and four oxygen atoms from the H2O molecules. Each uranium coordination polyhedron is connected via sulphate tetrahedra with other uranium polyhedra and through hydrogen bonds to the apices of sulphate tetrahedra.
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