The crystal structure of Cu2Pb6Bi8S19

The crystal structure of natural Cu2Pb6Bi8S19, space group C2/m, a = 27.64 Angstrom, b = 4.05 Angstrom, c = 20.74 Angstrom, beta = 131.26 degrees has been determined and refined to the value of R = 0.05 from 1488 reflections with I > 2 sigma(I) obtained on four-circle diffractometer equipped with a CCD area detector. It is composed of en echelon staggered fragments of (100 )(PbS) sulfide layers which are two atomic layers thick and alternate with periodically sheared (111)(PbS) layers; these are two octahedra thick. It i s built from ph coordination octahedra and bicapped trigonal prisms combine d with Bi in square pyramidal/asymmetric octahedral coordinations. Cu occur s in paired tetrahedra interconnecting the staggered (100)(PbS) fragments. Cu2Pb6Bi8S19 forms a homologous series with Cu2Pb3Bi8(S, Se)(16) (junoite) in which the sheared (111)(PbS) layers are one octahedron thick. Cu2Pb6Bi8S 19 is a new sulfosalt from Felbertal, Austria.