The crystal structure of watkinsonite Cu2PbBi4Se4 from the uranium deposit of Zalesi, czech republic

TY - JOUR

T1 - The crystal structure of watkinsonite Cu2PbBi4Se4 from the uranium deposit of Zalesi, czech republic

AU - Topa, D.

AU - Makovicky, Emil

AU - Sejkora, J.

AU - Dittrich, H.

PY - 2010/10

Y1 - 2010/10

N2 - The crystal structure of sulfur-free watkinsonite, ideally Cu 2PbBi4Se8, monoclinic, a 12.952(4), b 4.152(1), c 15.155(5) Å, β 108.93(1)°, space group P21/m, Z = 2, part of the selenide mineralization of the uranium deposit of Zálesí, Czech Republic, has been solved by direct methods and refined to R1 = 4.61% on the basis of 1287 unique reflections [F 0 > (4σ (F0)] collected on a Bruker P3 diffractometer with a CCD detector and MoKα radiation. The crystal structure contains one Pb site, four Bi sites, two Cu sites and eight Se sites. Partial replacement of one Cu (in a linearly coordinated site) by Ag is observed. The crystal structure consists of (100)pbs slabs four atomic planes thick of a galena-like structure alternating with single layers of hexagonally packed selenium. The Pb atoms form asymmetric bicapped coordination prisms embedded in the surfaces of the galena-like pseudotetragonal slabs; atoms Bi 1-3 occur as irregular coordination octahedra in the interior and at the surfaces of this slab. In addition, Bi4 forms a coordination prism similar to that of lead. Tetrahedrally coordinated copper Cu2 caps triangular voids of the hexagonal layer, whereas linearly coordinated Cu1 (with minor Ag), with the opposing Cu-Se bonds equal to 2.36 and 2.40 Å, respectively, forms foreshortened coordination octahedra, with four additional Cu-Se distances in the range 3.05-3.17 Å. The crystal structure of watkinsonite is closely related to that of berryite, Cu3Ag2Pb3Bi 7Si6, in which the foreshortened coordination octahedra are occupied by Ag, and Cu resides in the hexagonal layer.

AB - The crystal structure of sulfur-free watkinsonite, ideally Cu 2PbBi4Se8, monoclinic, a 12.952(4), b 4.152(1), c 15.155(5) Å, β 108.93(1)°, space group P21/m, Z = 2, part of the selenide mineralization of the uranium deposit of Zálesí, Czech Republic, has been solved by direct methods and refined to R1 = 4.61% on the basis of 1287 unique reflections [F 0 > (4σ (F0)] collected on a Bruker P3 diffractometer with a CCD detector and MoKα radiation. The crystal structure contains one Pb site, four Bi sites, two Cu sites and eight Se sites. Partial replacement of one Cu (in a linearly coordinated site) by Ag is observed. The crystal structure consists of (100)pbs slabs four atomic planes thick of a galena-like structure alternating with single layers of hexagonally packed selenium. The Pb atoms form asymmetric bicapped coordination prisms embedded in the surfaces of the galena-like pseudotetragonal slabs; atoms Bi 1-3 occur as irregular coordination octahedra in the interior and at the surfaces of this slab. In addition, Bi4 forms a coordination prism similar to that of lead. Tetrahedrally coordinated copper Cu2 caps triangular voids of the hexagonal layer, whereas linearly coordinated Cu1 (with minor Ag), with the opposing Cu-Se bonds equal to 2.36 and 2.40 Å, respectively, forms foreshortened coordination octahedra, with four additional Cu-Se distances in the range 3.05-3.17 Å. The crystal structure of watkinsonite is closely related to that of berryite, Cu3Ag2Pb3Bi 7Si6, in which the foreshortened coordination octahedra are occupied by Ag, and Cu resides in the hexagonal layer.

M3 - Journal article

SN - 0008-4476

VL - 48

SP - 1109

EP - 1118

JO - Canadian Mineralogist

JF - Canadian Mineralogist

IS - 5

ER -