Locality: Solongo B deposit, Vitim Plateau, Buriatia Republic (Buryatia), Transbaikalia (Zabaykalye), Eastern-Siberian Region, Russia Dimensions: 2.4 cm x 1.6 cm x 1.3 cm Frolovite is a very rare anhydrous borate, found in only three localities worldwide (MINDAT). Grayish-white frolovite is encased in the thumbnail matrix on this rare specimen from this unusual skarn deposit. Ex. Josef Vajdak Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Frolovite
Frolovite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ca[B(OH)₄]₂.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 3.5; specific gravity 2.14–2.22; Vitreous to dull luster; optically biaxial.
IMA symbol Flv, grandfathered status — known before the IMA’s founding, named in 1957.
A rare alteration product of hydrothermal boron minerals in skarn deposits.
It is found associated with Calciborite, calcite, gypsum, garnet, magnetite (Novofrolovskoye deposit, Russia); olshanskyite, parasibirskite, sibirskite, takedaite, pentahydroborite.
The name refers to the first-noted occurrence in the NovoFROLOVskoye deposit, Russia.