Owyheeite, Ag1.5Pb4.43Sb6.07S14, monoclinic and pseudo-orthorhombic, is invariably intimately twinned, and its structure displays an alternation of two types of unit order-disorder (OD) layers, with layer symmetries P(2/n) 2(1)/m 2(1)/m for the thicker OD layer, and P (1) 1 2(1)/m for the three-times thinner OD layer. These layers occur in two orientations, indexed as (021) and (0

2
1) of the owyheeite lattice. Ambiguity in the orientation of the thinner OD layer after the thicker one leads to intimate twinning (stacking disorder). Pseudohexagonality of the lattice (b × √3/2 ≈c) with two alternative sets of OD layers further complicates the twinning situation, which also can be described using a rod representation of the structure.

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