• journal_title：Mineralogical Magazine
• Contributor：L. Bindi ; P. Voudouris ; P. G. Spry
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2013-06-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2013.077.4.02
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：77
• issue：4
• firstpage：419
• section：Articles

The crystal structure of a Te-rich polybasite has been refined by means of X-ray diffraction data collected at room temperature (space group P3İm1; R = 0.0505 for 964 observed reflections and 94 parameters; refined formula Ag_14.46Cu_1.54Sb_1.58As_0.42S_9.67Te_1.33). The structure comprises stacking of [(Ag,Cu)₆(Sb,As)₂(S,Te)₇]²⁻ A and [Ag₉Cu(S,Te)₂(S,Te)₂]²⁺ B layer modules in which Sb forms isolated SbS₃ pyramids, as occurs typically in sulfosalts, Cu links two S atoms in a linear coordination and Ag occupies sites with coordination ranging from quasi linear to almost tetrahedral. The silver d¹⁰ ions are found in the B layer module along two-dimensional diffusion paths and their electron densities evidenced by means of a combination of a Gram-Charlier development of the atomic displacement factors and a split model. The Te-for-S substitution occurs at the same structural sites that Se substitutes for S in selenopolybasite and the Te occupancy at one of these sites is 0.49, thus suggesting the possibility that ‘telluropolybasite’ could be found in nature.