Te-rich canfieldite, AG8SN(S,TE)6, from the Legenbach Quarry, Binntal, Canton Valais, Switzerland: Occurrence, description and crystal structure.

In order to evaluate the effects of Te-for-S substitution in the minerals of the argyrodite group, the crystal structure and chemical composition of a crystal of Te-rich canfieldite from the Lengenbach quarry, Binntal, Switzerland, was investigated. The unit-cell parameters are a 11.0003(6) angstrom and V 1331.1(1) angstrom(3). The structure was solved and refined in the space group F (4) over bar 3m to R-1 = 0.0308 for 194 independent reflections and 21 parameters. Quantitative analysis led to the chemical formula Ag-8.05(Sn1.03Ge0.01)(Sigma 1.04)(S3.95Te1.95Se0.01)(Sigma 5.91), ideally Ag8Sn(S,Te)(6). The crystal structure of Te-rich canfieldite was found to be topologically identical to that of putzite, (Cu4.7Ag3.3)GeS6. Neglecting the short Ag-Ag contacts (due to disorder), the two Ag atoms in the structure can be considered as three-fold (Ag1) and four-fold (Ag2) coordinated. Tin adopts a regular tetrahedral coordination. The refinement of the site-occupancy factor indicates Te to be disordered over the three anion positions (i.e., X1, X2, and X3), with a preference for the X1 site.