gems, Ceylon, Sri Lanka, musgravite, taaffeite

Demartin and coauthors report the first known musgravite to have been fashioned as a faceted gemstone. The specimen, a 5.74 ct greenish-grey stone reportedly from Sri Lanka, was initially submitted for identification as a possible taaffeite. Gemological, chemical and X-ray investigations identified it as musgravite, a rare beryllium-magnesium-aluminium oxide closely related to taaffeite. The authors describe its refractive indices, specific gravity, optical character, absorption spectrum and chemical composition, and compare these properties with those of taaffeite. The identification demonstrated that musgravite, previously known principally as a rare mineral species, can occur as transparent material of sufficient size and quality for faceting.