On the homeotypes of kobellite

Abstract

Kobellite is a Pb-Bi-Sb sulfosalt with minor amounts of (Cu, Fe) and with the crystal structure composed of two types of rods, one of which has unusual lateral extensions (‘lobes’), which depart from the usual lozenge-shaped rod cross-section in sulfosalts. Several Pb-Bi-Sb and Pb-Sb-rich sulfosalts form a small group built on similar principles. Some of them are related by homology (e.g., izoklakeite), and differ by the perpendicular dimensions of rods (length and multiplicity of atomic layers in a rod; e.g., sterryite), and especially by different combinations of archetypes and archetype portions which participate in the rods (PbS archetype and the two orientations of SnS archetype). The present article summarizes and discusses the published data on the group. Homeotypism makes the group interesting and potentially a fertile source of further structural varieties.