Abstract
Cylindrite, a lead, tin, antimony, iron sulfosalt having a distinctive cylindrical morphology and a composite structure, is characterized by incommensurate structural modulations. It contains two types of sheets, and these have pseudohexagonal (H) and pseudotetragonal (T) structures with distinct lattice dimensions. The structure changes systematically from core to periphery of the crystals. The b and c axes of the H and T sheets are almost parallel to each other near the crystal cores. Further from the cores the angular divergence between the axes of the two types of sheets increases (i.e., the sheets are increasingly rotated relative to one another), and the wavelength of the structural modulation decreases. The crystal accommodates the dimensional misfit between the H and T sheets by a combination of this divergence, the variation of the structural modulation, and the curving of the layers.
