Almost white crystal aggregates of the rare mineral zirsinalite from one of the very few known locaities worldwide (Alluaiv Mountains, Lovozero, Kola, Russian Federation), all of them in Khibiny, Russia, — Photo: David Hospital · CC BY-SA 4.0
Zirsinalite
Zirsinalite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₆CaZrSi₆O₁₈.
It crystallizes in the hexagonal crystal system (space group R-3c). It is a member of the Lovozerite-Zirsinalite–Lovozerite structural group.
Key properties: Mohs hardness 5.5; specific gravity 2.88–2.92; Vitreous luster; optically uniaxial.
IMA symbol Zsl, IMA status: approved, named in 1973.
Found in pegmatitic veinlets cutting alkalic rocks in differentiated alkalic massifs.
It is found associated with Aegirine, lomonosovite, barian lamprophyllite, lovozerite, eudialyte (Mt. Koashva, Russia).
The name refers to ZIRconium, SIlicon, and sodium, NAtrium, in the composition.