Contribution
New data on cannizzarite and bursaite
Mozgova, N. N.; Organova, N. I.; Borodaev, Yu. S.; Ryabeva, E. G.; Sivtsov, A. V.; Getmanskaya, T. I.; Kuzmina, O. V.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 158 Heft 3 (1988), p. 293 - 309
27 références bibliographiques
publié: Feb 25, 1988
DOI: 10.1127/njma/158/1988/293
ArtNo. ESP154015803006, Prix: 29.00 €
Abstract
Two very rare Pb-Bi sulphosalts cannizzarite and bursaite were found in the Shumilovskoe Sn-W deposit (West Transbaikal). The minerals occur as platy elongated grains up to 1.0 mm long. Cannizzarite represents a Se-free low-Bi variety confirmed by microprobe data for the first time. Four electron microprobe analyses provide an average composition (Pb3.90Ag0.09)3.99(Bi5.09Sb0.11)5.20S11.31 close to the ideal formula of a low-Bi cannizzarite Pb4Bi5S11.5. Optically homogeneous grains with composition (Pb4,9Ag0.24)5.14(Bi3.97Sb0.06)4.03S10.81 (average of four microprobe analyses) corresponding to the bursaite formula Pb5Bi4S11, yield lillianite-like electron microdiffraction pictures and X-ray powder pattern. The latter contains more lines than lillianite standard. This powder data may be satisfactorily indexed with orthorhombic symmetry Bbmm supposing two lillianite-like phases (a = 13.42, b = 20.37, c = 4.12 Å and a = 13.55, b = 19.79, c = 4.04 Å) in the studied grains. The phases seem to be the exsolution products of non-stoichiometric phase III. The name “bursaite” is proposed to be retained for lillianite variety, which composition corresponds rather closely to Pb5Bi4S11.
Mots-clefs
Cannizzarite • bursaite • lillianite • cosalite • Pb-Bi sulphosalts • crystal structure • sublattices • microprobe analyses • reflectance • hardness • Shumilovskoe deposit; Transbaikal region