Parkerite, Shandite and Pašavaite structures

The new mineral pašavaite Pd3Pb2Te2

Mineral pašavaite Pd3Pb2Te2 displays orthorhombic symmetry, space group Pmmn. Its crystal structure is composed of [PdPb4Te2] distorted octahedra having Te atoms in a trans position with respect to one another. These octahedra are connected by face-sharing (parallel to b axis), edge-sharing (parallel to a axis) and corner-sharing (parallel to c axis).

The chemical composition of the mineral pašavaite, Pd3Pb2Te2, indicates a relationship to minerals parkerite (Ni3Bi2S2, C2/m) (Brower et al. 1974; Baranov et al. 2001) and shandite (Ni3Pb2S2, R 3m) (Brower et al. 1974). Despite the fact that these minerals have different symmetry, they show many structural similarities. As was pointed by Natarajan et al. (1988), shandite and parkerite structure show the same basic structural unit: a pseudocubic subcell with general formula AX of the CsCl type (A – Pb or Bi; X – S). Pašavaite contains the same structural motive; a pseudocubic subcell of Pb atoms centred by Te atoms, i.e. the cube of CsCl-type (Fig. 4).


Reference:  Applications of experimental mineralogy to Te containing systems: Crystal structures, phase relations


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