(A cannizzarite homological series.

Microprobe, SEM and XRD studies on cannizzarite from Lipari and from the Vysokogorskoe deposit are reported. Two samples from Lipari have compositions Pb4Bi5S11.5 and Pb4Bi4.3S10.75 respectively, while the Soviet specimen has the composition Pb4Bi6S13. The Italian Bi-poor cannizzarite has two sublattices: one (T) with a pseudotetragonal motif (a 4.12, b 4.1 A) and the other (H) with a pseudohexagonal motif (a 7.03, b 4.1 A). The Soviet material has a single lattice with an orthorhombic symmetry (Pmm) and a 20.70, b 4.16 A; it is a 3H/5T homologue, with different lattice parameters from those of the 27H/46T homologue.-R.A.H.