Vlasovite: Gemstones Information

Vlasovite is Na2ZrSi4O11 and has been found in transparent pale brown monoclinic (triclinic) crystals with greasy lustre, hardness 6 and SG 2.92–2.97. The RI for the alpha, beta and gamma rays is 1.605, 1.623,1.625, biaxial negative with birefringence 0.019. Vlasovite occurs as a late phase in nepheline syenites and syenitic pegmatites; faceted material from the Lovozero massif, Kola Peninsula, Russia, occurs along the con-tact zone of a differentiated alkalic massif.