Pezzottaite from Ambatovita, Madagascar: A New Gem Mineral
Pezzottaite, ideally Cs(Be2Li)Al2Si6O18, is a new gem mineral that is the Cs,Li–rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in central Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted stones and cat’s-eye cabochons that have been cut usually show a deep purplish pink color. Pezzottaite is distinguished from beryl by its higher refractive indices (typically no=1.615–1.619 and ne=1.607–1.610) and specific gravity values (typically 3.09–3.11). In addition, the new mineral’s infrared and Raman spectra, as well as its X-ray diffraction pattern, are distinctive, while the visible spectrum recorded with the spectrophotometer is similar to that of morganite. The color is probably caused by radiation-induced color centers involving Mn3+.
Table 1: Electron-Microprobe Analyses of Pezzottaite Done at the University of New Orleans
Table 2: Mn, Fe, and Ti Abundances in Pezzottaite and Red and Pink Beryls
Spectra: IR Absorption, Raman, and X-ray Diffraction
Submitted by Brendan M. Laurs
January 20, 2004