The crystal structure of ramdohrite Pb_5.9Fe_0.1Mn_0.1In_0.1Cd_0.2Ag_2.8Sb_10.8S₂₄: a new refinement

TY - JOUR

T1 - The crystal structure of ramdohrite Pb5.9Fe0.1Mn0.1In0.1Cd0.2Ag2.8Sb10.8S24

T2 - a new refinement

AU - Makovicky, Emil

AU - Mumme, William G.

AU - Gable, Robert W.

PY - 2013/4

Y1 - 2013/4

N2 - The crystal structure of ramdohrite, Pb5.9Fe 0.1Mn0.1In0.1Cd0.2Ag 2.8Sb10.8S24, from the Chocaya mine, Potosí, Bolivia, determined by Makovicky and Mumme from film data in 1983, was refined from single-crystal diffractometer data to the R value 0.060, based on 5230 reflections [I < 2s(I)] from a twinned crystal. Lattice parameters are a = 8.7348(3), b = 13.0543(4), c = 19.3117(6) Å, and β = 90.179(2)°, space group P21/n. Two bicapped trigonal prismatic sites of lead bridge and unite adjacent (311)PbS slabs. These slabs contain five distinct coordination pyramids of Sb with trapezoidal cross sections, a mixed and disordered Sb-Ag-Cd-(Pb) site, refined as 0.39 Sb + 0.61 Ag, a pure Ag site with a very open, irregular tetrahedral coordination, and an octahedral site occupied by Pb. The (311)PbS slabs contain large lone electron pair micelles formed by four distinct antimony sites in alternation with small such micelles formed by a single Sb site. The geometric arrangement of these slabs is not based on crankshaft chains of short, strong Me-S bonds but on a chess-board arrangement of (predominantly) Sb pairs that share two common S atoms via short bonds. Relationships to, and differenced from, fizelyite and uchucchacuaite are described and discussed.

AB - The crystal structure of ramdohrite, Pb5.9Fe 0.1Mn0.1In0.1Cd0.2Ag 2.8Sb10.8S24, from the Chocaya mine, Potosí, Bolivia, determined by Makovicky and Mumme from film data in 1983, was refined from single-crystal diffractometer data to the R value 0.060, based on 5230 reflections [I < 2s(I)] from a twinned crystal. Lattice parameters are a = 8.7348(3), b = 13.0543(4), c = 19.3117(6) Å, and β = 90.179(2)°, space group P21/n. Two bicapped trigonal prismatic sites of lead bridge and unite adjacent (311)PbS slabs. These slabs contain five distinct coordination pyramids of Sb with trapezoidal cross sections, a mixed and disordered Sb-Ag-Cd-(Pb) site, refined as 0.39 Sb + 0.61 Ag, a pure Ag site with a very open, irregular tetrahedral coordination, and an octahedral site occupied by Pb. The (311)PbS slabs contain large lone electron pair micelles formed by four distinct antimony sites in alternation with small such micelles formed by a single Sb site. The geometric arrangement of these slabs is not based on crankshaft chains of short, strong Me-S bonds but on a chess-board arrangement of (predominantly) Sb pairs that share two common S atoms via short bonds. Relationships to, and differenced from, fizelyite and uchucchacuaite are described and discussed.

U2 - 10.2138/am.2013.4146

DO - 10.2138/am.2013.4146

M3 - Journal article

SN - 0003-004X

VL - 98

SP - 773

EP - 779

JO - American Mineralogist

JF - American Mineralogist

IS - 4

ER -