The crystal structure of barikaite
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The crystal structure of barikaite. / Makovicky, Emil; Topa, Dan.
I: Mineralogical Magazine, Bind 77, Nr. 8, 2013, s. 3093-3104.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - The crystal structure of barikaite
AU - Makovicky, Emil
AU - Topa, Dan
PY - 2013
Y1 - 2013
N2 - Electron microprobe analysis of barikaite (Topa et al., 2013) indicates the chemical formula Ag2.90Tl0.04Pb9.31As11.26Sb8.12S40.37. Barikaite is monoclinic, with a 8.533(1) Å, b 8.075(1) Å, c 24.828(2) Å, and β 99.077(1)°; unit-cell volume 1689.2 Å3 and the space-group setting is P21/n. This compares well with the unit-cell parameters of rathite Pb10Tl0.9As17.9Sb1.3Ag2S40 from the Lengenbach deposit with the same lattice setting. Barikaite is a member of sartorite homologous series (N = 4). The unit cell of barikaite contains eight cation sites and ten anion sites. Four of the cation sites have mixed occupancies – the split sites As2–Sb2, As3–Sb3, Ag5–As5 and the site Me6 with three cations involved. Two of the lead sites, Pb1 and Pb2, display tricapped trigonal prismatic coordinations and alternate along the 8.53 Å a direction. They form zig-zag walls parallel to (001). There are three distinct [100] columns of alternating cations, As1–(As,Sb)2, Sb4–(As,Sb)3 and (As,Ag)5–(Pb,Sb)6 which together form trapezoidally configured single (013) layers. These layers aggregate into tightly-bonded double layers, separated by lone electron pair micelles. In barikaite, the predominantly As-occupied and Sb-occupied sites are distributed in a chess-board-like scheme
AB - Electron microprobe analysis of barikaite (Topa et al., 2013) indicates the chemical formula Ag2.90Tl0.04Pb9.31As11.26Sb8.12S40.37. Barikaite is monoclinic, with a 8.533(1) Å, b 8.075(1) Å, c 24.828(2) Å, and β 99.077(1)°; unit-cell volume 1689.2 Å3 and the space-group setting is P21/n. This compares well with the unit-cell parameters of rathite Pb10Tl0.9As17.9Sb1.3Ag2S40 from the Lengenbach deposit with the same lattice setting. Barikaite is a member of sartorite homologous series (N = 4). The unit cell of barikaite contains eight cation sites and ten anion sites. Four of the cation sites have mixed occupancies – the split sites As2–Sb2, As3–Sb3, Ag5–As5 and the site Me6 with three cations involved. Two of the lead sites, Pb1 and Pb2, display tricapped trigonal prismatic coordinations and alternate along the 8.53 Å a direction. They form zig-zag walls parallel to (001). There are three distinct [100] columns of alternating cations, As1–(As,Sb)2, Sb4–(As,Sb)3 and (As,Ag)5–(Pb,Sb)6 which together form trapezoidally configured single (013) layers. These layers aggregate into tightly-bonded double layers, separated by lone electron pair micelles. In barikaite, the predominantly As-occupied and Sb-occupied sites are distributed in a chess-board-like scheme
U2 - 10.1180/minmag.2013.077.8.04
DO - 10.1180/minmag.2013.077.8.04
M3 - Journal article
VL - 77
SP - 3093
EP - 3104
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 8
ER -
ID: 99342699