Summary: Xocomecatlite and tlalocite were found at the Bambollita mine near Moctezuma, Sonora. Xocomecatlite is probably orthorhombic, and an indexed cell based on the powder data gave a 12·140 Å, b 14·318, c 11·662. Based on this cell, the empirical contents are Cu35·6 Zn1·7 (TeO4)12·5 (OH)51·6 or Cu3TeO4(OH)4. Tellurate was found both microchemically and by spectrophotometry. Colour rich green (R.H.S. 132A) with pale streak, H = 4. Optically negative with α = 1·775, β = 1·900, γ = 1·920. G = 4·65.
Tlalocite is optically orthorhombic but the cell could not be indexed; only powder data are presented. Chemical analysis showed both tellurite and tellurate and led to the formula Cu10Zn6(TeO3)(TeO3)(TeO)(TeO4)2Cl(OH)25·27H2O.
Colour pale blue (R.H.S. 121A) with a whitish streak; H = 1, gummy and sectile. G = 4·55.
Plotting stability fields for various Te species at 25 °C in terms of Eh and pH showed that TeO42−·aq can exist in nature over a wide pH range, but only under extreme conditions of oxidation.