A dark brown single crystal of the rare mineral sobolevite from the famous Kola region in Russia (Alluaiv Mountain, Lovozero Massif, Murmansk Oblast, Russian Federation). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Sobolevite
Sobolevite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₆(Na₂Ca)(NaCaMn)Na₂Ti₂Na₂(TiMn)(Si₂O₇)₂(PO₄)₄O₂(OF)F₂.
It crystallizes in the monoclinic crystal system (space group Pc). It is a member of the Seidozerite-Murmanite structural group.
Key properties: Mohs hardness 4.5–5; specific gravity 3.03; Metallic, resinous, or pearly on (001) luster; optically biaxial.
IMA symbol Sob, IMA status: approved, named in 1982.
Found in alkalic pegmatite, cutting sodalite-cancrinite syenite, in a differentiated alkalic massif.
It is found associated with Lamprophyllite, lomonosovite.
The name refers to Academician Vladimir Stepanovich Sobolev (1908–1982), Russian mineralogist, petrologist, and former President of the International Mineralogical Association.