The crystal structure of Cu2Pb6Bi8S19

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.