White crystal aggregates of the very rare mineral kumtyubeite from Urals (Kopeisk, Chelyabinsk Oblast, Russian Federation). Only very few localities known worldwide. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Kumtyubeite
Kumtyubeite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₅(SiO₄)₂F₂.
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Humite structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.866; Vitreous luster; optically biaxial.
IMA symbol Kty, IMA status: approved, named in 2008.
A rock-forming mineral in contact-metasomatic, spurrite-rondorfite-ellestadite skarn in carbonate-xenoliths in ignimbrites.
It is found associated with Rondorfite, lakargiite, kimzeyite, srebrodolskite, bultfonteinite, Ca-hydrosilicates, ettringite.
Derives from Kum-Tyube, the name of a mountain plateau near where the mineral was found.