Rod-based sulphosalt structures derived from the SnS and PbS archetypes
European Journal of Mineralogy Volume 5 Number 3 (1993), p. 545 - 592
veröffentlicht: Jun 14, 1993
Manuskript akzeptiert: Dec 8, 1992
Manuskript erhalten: Feb 13, 1991
ArtNo. ESP147050503018, Preis: 29.00 €
Abstract In the present review on the rod-based sulphosalt structures we describe the fundamental features of their large- to medium-scale crystal chemistry. The principal, lozenge-shaped rods in these structures represent portions based on the SnS or PbS archetype, with their surfaces being alternatively of the pseudotetragonal or pseudohexagonal (often sheared) type. The formation of the rod-based sulphosalt structures can then be understood as a recombination of these rods into a structure by means of non-commensurate Q: H interfaces. All of these structures show distinct accumulation of Sb and Bi in rod interiors (that represent the lone electron pair micelles) and of Pb (and other large cations) on the pseudotetragonal surfaces of the lozenge-shaped rod. Detailed analysis is given of the first largest category of rod-based sulphosalt structures, those based on rods interconnected into layers. Twelve different types of such layers have been recognized, based primarily on the mode of interconnection of the rods into layers; further subdivision in each category reflects the characteristic dimensions of their lozenge-shaped cross-sections. All these derivations result in characteristic geometry and stoichiometry of these structures, treated here in some detail. A survey of matches and combinations of different rod-layer types observed or envisageable during the structure-recombination process concludes the part on rod-layer based structures. The second part of the review starts with a survey of pure (i.e. not layer-like) rod-based sulphosalt structures and proceeds to lay out classification principles for the three fundamental categories of rod-based structures: (1) the layer-, (2) the chess-board, and (3) the cyclic category, with the suggestions for their further subdivision. The present review deals with the most important Pb-Sb, Sn-Sb, Pb-Bi-Sb as well as the selected Pb-Bi, Ba-Bi and other sulphosalts, eventually with minor contents of Cu or Fe.