Cervelleite, Ag4TeS, a new mineral from the Bambolla mine, Mexico, and a description of a photo-chemical reaction involving cervelleite, acanthite and hessite
Criddle, Alan J.; Chisholm, Jim E.; Stanley, Chris J.
European Journal of Mineralogy Volume 1 Number 3 (1989), p. 371 - 380
published: Jul 27, 1989
manuscript accepted: Jan 25, 1989
manuscript received: Dec 21, 1988
ArtNo. ESP147050103008, Price: 29.00 €
Abstract Cervelleite, Ag4TeS, is a new mineral from the Bambolla mine, Moctezuma, Sonora, Mexico. It occurs as thin, 30 μm rims surrounding acanthite in hessite and as vermiform inclusions in the latter. Isotropic and opaque ; in plane-polarized light, it is slightly bluish to slightly greenish white. Colour values (for CIE illuminant C) are: x 0.302, y 0.311, Y% 37.8, λd482, Pe% 3.5. A Vickers microhardness value (VHN10) is 26. The strongest reflections in the X-ray powder pattern are [dhklin Å (I) (hkl)] : 6.29 (s) (012), 5.00 (vvs) (022), 4.64 (m) (122,003), 4.24 (vs) (113), 3.766 (ms) (123). The reflections are indexable in terms of a primitive cubic cell with α 14.03(1) Å and probable contents 24[Ag4TeS], giving a calculated density of 8.53 g.cm-3. Averaged electron microprobe analyses gave: Ag 73.0, Cu 0.1, Te 22.2, S 5.3, total 100.6 wt%. Cervelleite, acanthite and hessite are altered rapidly and profoundly by light, in a surface reaction interpreted as photo-chemical in origin.