FIG. 1. The cuprobismutite series and related padraite, according to (a) Makovicky (1989) and (b) Mumme (1986). Padraite shares the common Cu₈Bi₈S₁₆ layer with members of the cuprobismutite series. In the padraite structure (b, right), the D module has variable thickness along the c axis: either one octahedron thick at the T contact, or two octahedra thick along the trigonal-tetrahedral match. In each drawing, atoms are, in decreasing size, S, Bi and Cu. In the drawings for padraite, the order is Pb, S, Bi, Ag and Cu.