Pezzottaite from Ambatovita, Madagascar: A New Gem Mineral

Abstract

Pezzottaite, ideally Cs(Be2Li)Al2Si6O18, is a new gem mineral that isthe Cs,Li-rich member of the beryl group. It was discovered in November2002 in a granitic pegmatite near Ambatovita in central Madagascar. Onlya few dozen kilograms of gem rough were mined, and the deposit appearsnearly exhausted. The limited number of transparent faceted stones andcat's-eye cabochons that have been cut usually show a deep purplish pinkcolor. Pezzottaite is distinguished from beryl by its higher refractiveindices (typically n(o)=1.615-1.619 and n(e)=1.607-1.610) and specificgravity values (typically 3.09-3.11). In addition, the new mineral'sinfrared and Raman spectra, as well as its X-ray diffraction pattern,are distinctive, while the visible spectrum recorded with thespectrophotometer is similar to that of morganite. The color is probablycaused by radiation-induced color centers involving Mn3+.