Brown crystals of this rare niobium mineral belkovite from the type locality in Russia (Vuoriyarvi Massif, Northern Karelia, Murmansk Oblast, Russian Federation). Only two known localities worldwide. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Belkovite
Belkovite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ba₃Nb₆(Si₂O₇)₂O₁₂.
It crystallizes in the hexagonal crystal system (space group P-62m).
Key properties: Mohs hardness 6–7; specific gravity 4.16; White streak; Adamantine luster; optically uniaxial.
IMA symbol Bkv, IMA status: approved, named in 1989.
Of secondary origin, produced through alteration of barium-rich pyrochlore during dolomitization of calcite carbonatites in pyroxenites.
It is found associated with Magnetite, pyrochlore, phlogopite, chlorite, pyrite, pyrrhotite, dolomite, carbonate-apatite, barite, alstonite, nenadkevichite.
The name refers to Igor Vladimirovich Bel'kov (1917–1989), Soviet mineralogist, Director, Kola Scientific Center, Apatity, Russia, who explored the Kola Peninsula.