Lab Notes Gems & Gemology, Fall 2019, Vol. 55, No. 3


A 1.20 ct faceted vlasovite.
Figure 1. This 1.20 ct octagonal modified brilliant was identified as the rare gem vlasovite. Photo by Diego Sanchez.

The Carlsbad laboratory recently received for identification service a stone with properties that were not consistent with stones previously identified at GIA. This yellow octagonal modified brilliant (figure 1), measuring 6.41 × 5.26 × 4.68 mm, weighed 1.20 ct and had a specific gravity of 3.01. Microscopic features observed included distinct parallel twinning planes (figure 2), iridescent fractures, stringers, and fingerprints. Standard gemological testing revealed that it was doubly refractive, with a biaxial optic figure and a refractive index of 1.608–1.628. It fluoresced a very weak yellow under short-wave UV and had no reaction under long-wave UV. The Raman spectrum of the stone (figure 3) was matched to one in the RRUFF database, which confirmed the gem’s identity as vlasovite, an inosilicate mineral with the chemical formula Na2ZrSiO4O11 (

Colorful twinning planes seen in the faceted vlasovite.
Figure 2. Colorful twinning planes were observed in the faceted vlasovite using polarized light. Photomicrograph by Jessa Rizzo; field of view 3.23 mm.
Raman spectroscopy confirmed vlasovite.
Figure 3. Raman spectroscopy confirmed the gem’s identity as vlasovite.

Vlasovite is known to be found in pegmatites in northern Russia, Canada, and Portugal. It was named after Kuzma Alekseevich Vlasov, who studied the region where vlasovite originated ( Vlasovite is a rare mineral, and faceted stones are especially rare. This is the first faceted example examined at GIA’s Carlsbad laboratory.

Jessa Rizzo is a staff gemologist at GIA in Carlsbad, California.