The crystal structure of Cu (sub 2) Pb (sub 6) Bi (sub 8) S (sub 19)

The crystal structure of natural Cu (sub 2) Pb (sub 6) Bi (sub 8) S (sub 19) , space group C2/m, a = 27.64Aa, b = 4.05Aa, c = 20.74Aa, beta = 131.26 degrees , has been determined and refined to the value of R = 0.05 from 1488 reflections with I>2sigma (sub 1) obtained on four-circle diffractometer equipped with a CCD area detector. It is composed of en echelon staggered fragments of (100) (sub PbS) sulfide layers which are two atomic layers thick and alternate with periodically sheared (111) (sub PbS) layers; these are two octahedra thick. It is built from Pb coordination octahedra and bicapped trigonal prisms combined with Bi in square pyramidal/asymmetric octahedral coordinations. Cu occurs in paired tetrahedra interconnecting the staggered (100) (sub PbS) fragments. Cu (sub 2) Pb (sub 6) Bi (sub 8) S (sub 19) forms a homologous series with Cu (sub 2) Pb (sub 3) Bi (sub 8) (S, Se) (sub 16) (junoite) in which the sheared (111) (sub PbS) layers are one octahedron thick. Cu (sub 2) Pb (sub 6) Bi (sub 8) S (sub 19) is a new sulfosalt from Felbertal, Austria.