Cylindrite (Pb, Sn)[.sub.8][Sb.sub.4][Fe.sub.2][Sn.sub.5][S.sub.27]
Cylindrite occurs in a unique habit consisting of very thin, leadgray folia rolled up into cylinders.
Vuggy masses of franckeite lined with drusy franckeite crystals from 2 to 5 mm are currently the main ore in one portion of the Contacto vein, where franckeite is associated with pyrite, arsenopyrite, wurtzite and rare cylindrite. It also occurs abundantly in the Plata vein.
Franckeite and cylindrite are almost invariably associated with some stannite (Bandy, 1944).
The cylindrite structure has been interpreted as consisting of incommensurable alternating layers of pseudo-tetragonal and pseudo-hexagonal symmetry.
An example is "cylindrite <homologue (19,13)Q/(30,12)H>" for a homologue of the cylindrite series with a tetragonal (quadratic) building block of 19 by 13 units which is commensurable with a hexagonal block of 30 by 12 units.