TY - JOUR
T1 - Comparative crystal-structure study of Ag-free lilliantite and galenobismutite from vulcano, Aeolian Islands, Italy
AU - Pinto, Daniela
AU - Balic Zunic, Tonci
AU - Garavelli, Anna
AU - Makovicky, Emil
AU - Vurro, Filippo
PY - 2006
Y1 - 2006
N2 - The crystal structures of natural Ag-free lillianite of fumarolic origin from Vulcano, Aeolian Islands, Italy, Pb2.88Bi2.12(S5.67 Se0.33)S6.00, with a 13.567(1), b 20.655(2), c 4.1216(4) Å, V 1155.0(2) Å3, space group Bbmm, Z = 4, and galenobismutite also from Vulcano, Pb1.00Bi2.03(S3.87Se0.11)¿3.98, with a 11.815(2), b 14.593(2), c 4.0814(6) Å, V 703.7(2) Å3, space group Pnam, Z = 4, were refined from single-crystal X-ray data. The refi nements converge to R = 3.40% [for 745 refl ections with Fo > 4(Fo)], and R = 2.96% [for 607 reflections with Fo > 4(Fo)] for Ag-free lillianite and galenobismutite, respectively. In Ag-free lillianite, the trigonal prism M3 is occupied only by Pb, whereas both the octahedrally coordinated M1 and M2 sites are mixed (Pb,Bi) positions. The same octahedra incorporate both the surplus of Bi and vacancies () created by the substitution 3Pb2+ ¿ 2Bi3+ + , which allows for the observed deviations from the ideal composition, Pb3Bi2S6. Selenium is preferentially ordered at the six-fold and fi ve-fold coordinated anionic sites, whereas the four-fold coordinated site S3 remains free of Se. The known structural arrangement of galenobismutite was confi rmed in this work. The octahedrally coordinated M1gb site was found to be a ful Bi position. Some evidence of Pb-Bi disorder has been observed at both the M2gb (Bi-dominated) and M3gb (Pb-dominated)positions. A heterogeneous distribution of Se in the anionic S sites was observed in galenobismutite. Atoms of Se are mainlyconcentrated at the site S1, and less so in the other anionic sites.
AB - The crystal structures of natural Ag-free lillianite of fumarolic origin from Vulcano, Aeolian Islands, Italy, Pb2.88Bi2.12(S5.67 Se0.33)S6.00, with a 13.567(1), b 20.655(2), c 4.1216(4) Å, V 1155.0(2) Å3, space group Bbmm, Z = 4, and galenobismutite also from Vulcano, Pb1.00Bi2.03(S3.87Se0.11)¿3.98, with a 11.815(2), b 14.593(2), c 4.0814(6) Å, V 703.7(2) Å3, space group Pnam, Z = 4, were refined from single-crystal X-ray data. The refi nements converge to R = 3.40% [for 745 refl ections with Fo > 4(Fo)], and R = 2.96% [for 607 reflections with Fo > 4(Fo)] for Ag-free lillianite and galenobismutite, respectively. In Ag-free lillianite, the trigonal prism M3 is occupied only by Pb, whereas both the octahedrally coordinated M1 and M2 sites are mixed (Pb,Bi) positions. The same octahedra incorporate both the surplus of Bi and vacancies () created by the substitution 3Pb2+ ¿ 2Bi3+ + , which allows for the observed deviations from the ideal composition, Pb3Bi2S6. Selenium is preferentially ordered at the six-fold and fi ve-fold coordinated anionic sites, whereas the four-fold coordinated site S3 remains free of Se. The known structural arrangement of galenobismutite was confi rmed in this work. The octahedrally coordinated M1gb site was found to be a ful Bi position. Some evidence of Pb-Bi disorder has been observed at both the M2gb (Bi-dominated) and M3gb (Pb-dominated)positions. A heterogeneous distribution of Se in the anionic S sites was observed in galenobismutite. Atoms of Se are mainlyconcentrated at the site S1, and less so in the other anionic sites.
KW - Faculty of Science
KW - Italien
KW - vulkan
KW - krystal strukturer
KW - Ag-free lillianite
KW - Italy
KW - Vulcano
KW - fumaroles
KW - crystal structure
KW - galenobismutite
M3 - Journal article
SN - 0008-4476
VL - 44
SP - 159
EP - 175
JO - Canadian Mineralogist
JF - Canadian Mineralogist
ER -