Alluaivite
A rare member of the eudialyte group and the group's only titanium silicate — its relatives are zirconium silicates.
Intro adapted from Wikipedia (CC BY-SA).
Alluaivite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₁₉(Ca,Mn²⁺)₆(Ti,Nb)₃Si₂₆O₇₄Cl·2H₂O.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Eudialyte structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.76; Vitreous luster; refractive index 1.625; optically uniaxial.
IMA symbol Aav, IMA status: approved, named in 1988.
Found in ultra-agpaitic pegmatites in a differentiated alkalic massif.
It is found associated with Eudialyte, nepheline, sodalite, potassic feldspar, arfvedsonite, aegirine.
The name refers to its occurrence on Mt. Alluaiv, Kola Peninsula, Russia.