Alluaivite is an exceedingly rare mineral of the eudialyte group, with complex formula written as Na19(Ca, Mn)6(Ti, Nb)3Si26O74Cl·2H2O. It is named after Mt. Alluaiv in Lovozero Tundry massif, Kola Peninsula, Russia, where it is found in ultra-agpaitic, hyperalkaline pegmatites.
It is unique among the eudialyte group as the only titanosilicate (other representatives of the group are usually zirconosilicates). The two dual-nature minerals of the group, being both titano- and zirconosilicates, are labyrinthite and dualite. They both contain alluaivite module in their structures.
- Category: Silicate mineral, Cyclosilicate
- Formula: Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O
- Crystal system: Trigonal
- Crystal class: Hexagonal scalenohedral (3m)
Occurrence and association
Alluaivite was found in ultra-agpaitic (highly alkaline) pegmatites on Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia – hence its name. Associating minerals are aegirine, arfvedsonite, eudialyte, nepheline, potassic feldspar, and sodalite.
- Color: Colorless to weak brownish pink
- Crystal habit: irregular accumulations
- Cleavage: None
- Fracture: Conchoidal
- Tenacity: Brittle
- Mohs scale hardness 5-6
- Luster: Vitreous
- Streak: White
- Diaphaneity: Transparent
- Density: 2.76 (measured)