Mcalpineite from the Gambatesa mine, Italy, and redefinition of the species

Mcalpineite has been found in the Gambatesa mine (eastern Liguria, Italy). It occurs in a quartz vein mainly as yellowish green earthy crusts consisting of poorly crystallized mcalpineite intergrown with an unidentified Cu-Te phase, as well as quite pure aggregates of well euhedral emerald green crystals (individually reaching up to 50 μm), associated with black fragments of paratellurite (TeO 2 ) and weissite (Cu 2-x Te). The chemical formula of this rare mineral, found at the McAlpine mine (typelocality; California, U.S.A.) and at the Centennial Eureka mine (Utah, U.S.A., co-type locality), was originally given Cu 3 TeO 6 ·H 2 O. X‑ray powder diffraction and selected-area electron diffraction data of mcalpineite are in good agreement with those of synthetic Cu 3 TeO 6 . In addition no evidence for structural OH group was detected by micro-Raman analysis carried out on samples from Gambatesa, Centennial Eureka, and McAlpine (co-type sample) mines. Taking into account structural, topological, and experimental evidence, the crystal structure and chemical composition of mcalpineite must be revised: the mineral crystallizes in the Ia3̄ space group and the correct chemical formula is Cu 3 TeO 6 .