Crystal chemistry and crystallography of some minerals in the tetradymite group Available to Purchase

Selen-tellurium is a mixture of the minerals selenium and tellurium. The atoms in stibarsen are ordered (completely or partially) so that the correct chemical formula is AsSb. Matildite AgBiS₂, bohdanowiczite AgBiSe₂, and volynskite AgBiTe₂, show atomic ordering in space group P3̄m1 with unit-cell dimensions similar to those of tsumoite, BiTe. The S and Te atoms are apparently disordered in ingodite to yield the chemical formula Bi(S,Te) and in sulphotsumoite to yield the chemical formula Bi(Te,S). The unnamed mineral of Aksenov et al. (1968) seems to be tellurian tsumoite, (Bi_0.58Te_0.42)Te. The synthetic composition of Godovnikov et al. (1966) is equivalent to bismuthian tsumoite, Bi(Te_0.75Bi_0.25). Platynite is possibly plumbian sulfurian nevskite, (Bi_0.650Pb_0.345)(Se_0.657S_0.348).

Kawazulite, Bi₂SeTe₂, is isostructural with tetradymite. Csiklovaite is a mixture of tetradymite and bismuthinite. The chemical formula of skippenite is probably Bi₂(Se,Te,S)₃, like that of tellurian paraguanajuatite. The Se and S are disordered in laitakarite to yield the chemical formula Bi₄(Se,S)₃. As S and Te ordering was not observed in josëite or josëite-B, there is possibly a complete solid solution series from tellurian ikunolite, Bi₄(S,Te)₃, to sulfurian pilsenite, Bi₄(Te,S)₃. The unnamed mineral of Yingchen (1986) is apparently tellurian ikunolite. Rucklidgeite, Bi₃Te₄, has an antipilsenite, Bi₄Te₃, structure type. The unnamed mineral of Harañczyk (1978) is rucklidgeite.