Abstract

The crystal structure of natural Cu2Pb6Bi8S19, space group C2/m, a = 27.64Å, b = 4.05Å, c = 20.74Å, β = 131.26°, has been determined and refined to the value of R = 0.05 from 1488 reflections with I > 2σ1 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 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)PbS fragments. Cu2Pb6Bi8S19 forms a homologous series with Cu2Pb3Bi8(S, Se)16 (junoite) in which the sheared (111)PbS layers are one octahedron thick. Cu2Pb6Bi8S19 is a new sulfosalt from Felbertal, Austria.

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