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Association twinnite-zinkénite-plagionite du gisement complexe à Sb-Pb-Zn de Rujevac (Yougoslavie)

1983; Volume: 106; Issue: 5 Linguagem: Inglês

10.3406/bulmi.1983.7730

0180-9210

Yves Moëlo, Youri S. Borodaev, N. N. Mozgova,

Metal Extraction and Bioleaching

Plagionite formed after robinsonite at Rujevac (Yugoslavia) contains late-stage twinnite associated with zinckenite. Microprobe analysis shows that As content, very low in robinsonite (0.3 %, i.e. As/(As + Sb) = 1.3 at. %), is higher in plagionite, between 1.0 and 3.1% (i.e. As/(As + Sb) from 4.4 to 10.5 at. %). Zinckenite and twinnite compositions are homogeneous, demonstrating mineral equilibrium between these two phases : As content of zinckenite is about 3.3 % (As/(As + Sb) = 12.0 at. %), while As/(As + Sb) ratio of twinnite is particularly low (25.3 at. %), near to the stoechiometric composition Pb2Sb3AsS8. The As/(As + Sb) ratios of coexisting twinnite and zinckenite seem strongly temperature-dependent ; especially, the maximum atomic substitution of Sb for As in twinnite increases with decreasing temperature. From a crystal chemical point of view, this change would reflect the incorporation of Sb3+ in a three-fold rather than five-fold coordination with decreasing temperature.