Proudite: a redetermination of its crystal structure and the proudite-felbertalite homologous series

TY - JOUR

T1 - Proudite

T2 - a redetermination of its crystal structure and the proudite-felbertalite homologous series

AU - Mumme, William G.

AU - Topa, D.

AU - Makovicky, Emil

PY - 2009

Y1 - 2009

N2 - The crystal structure of proudite was redetermined with the holotype material from Tennant Creek, Australia, using a Nonius single-crystal diffractometer and MoK radiation. Our determination of the structure, based on 3388 observed reflections, yielded an R1 value of 8.2% for 306 parameters. Proudite is monoclinic, a 31.814(1), b 4.1002(2), c 36.560(1), ß 109.266(1)° and space group C2/m. Results of new electron-microprobe analyses give its composition as Cu1.9Ag0.1Pb15.6Bi20.4Sb0.1S32.4Se14.5. We report analytical data for associated phases and for Se-free proudite from Felbertal, Austria, as well. The crystal structure contains 18 large cation sites (Pb, Bi, and mixed positions), a single Cu site, and 24 anion sites, nearly all of them being mixed Se,S sites. It consists of regularly sheared double-layers of octahedra that alternate with stepwise sheared (100)PbS layers, two cation-anion sheets thick. Each straight portion of the former layers is 10 octahedra wide, whereas each straight interval of the PbS-like layers is eight square coordination pyramids (Pb, Bi) wide. Proudite is the highest known member of a homologous series of Pb-Bi- Cu sulfosalts with a mixed character, combining accretion of polyhedra and variable-fit of two layer-type fragments. This series contains proudite, felbertalite, makovickyite and a hypothetical intermediate member not yet known as a pure member, only as a combination with a "makovickyite-like element" in a synthetic selenide. This series is here defined as the proudite-felbertalite homologous series.

AB - The crystal structure of proudite was redetermined with the holotype material from Tennant Creek, Australia, using a Nonius single-crystal diffractometer and MoK radiation. Our determination of the structure, based on 3388 observed reflections, yielded an R1 value of 8.2% for 306 parameters. Proudite is monoclinic, a 31.814(1), b 4.1002(2), c 36.560(1), ß 109.266(1)° and space group C2/m. Results of new electron-microprobe analyses give its composition as Cu1.9Ag0.1Pb15.6Bi20.4Sb0.1S32.4Se14.5. We report analytical data for associated phases and for Se-free proudite from Felbertal, Austria, as well. The crystal structure contains 18 large cation sites (Pb, Bi, and mixed positions), a single Cu site, and 24 anion sites, nearly all of them being mixed Se,S sites. It consists of regularly sheared double-layers of octahedra that alternate with stepwise sheared (100)PbS layers, two cation-anion sheets thick. Each straight portion of the former layers is 10 octahedra wide, whereas each straight interval of the PbS-like layers is eight square coordination pyramids (Pb, Bi) wide. Proudite is the highest known member of a homologous series of Pb-Bi- Cu sulfosalts with a mixed character, combining accretion of polyhedra and variable-fit of two layer-type fragments. This series contains proudite, felbertalite, makovickyite and a hypothetical intermediate member not yet known as a pure member, only as a combination with a "makovickyite-like element" in a synthetic selenide. This series is here defined as the proudite-felbertalite homologous series.

KW - Faculty of Science

KW - proudite

KW - krystalstrukturer

KW - proudite

KW - proudite–felbertalite homologous series

KW - crystal structure

U2 - 10.3749/canmin.47.1.25

DO - 10.3749/canmin.47.1.25

M3 - Journal article

SN - 0008-4476

VL - 47

SP - 25

EP - 38

JO - Canadian Mineralogist

JF - Canadian Mineralogist

ER -