Pezzottaite from Ambatovita, Madagascar: A New Gem Mineral

Brendan M. Laurs, William B. (Skip) Simmons, George R. Rossman, Elizabeth P. Quinn, Shane F. McClure, Adi Peretti, Thomas Armbruster, Frank C. Hawthorne, Alexander U. Falster, Detlef Günther, and Mark A. Cooper, and Bernard Grobéty

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 n_o=1.615–1.619 and n_e=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⁺.

DATA DEPOSITORY

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