Alluaivite
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CategorySilicate mineral, Cyclosilicate
FormulaNa19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O
Strunz classification9.CO.10 (10 ed)
8/E.25-40 (8 ed)
8/E.25-40 (8 ed)
| Alluaivite | |
|---|---|
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula | Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O |
| IMA symbol | Aav[1] |
| Strunz classification | 9.CO.10 (10 ed) 8/E.25-40 (8 ed) |
| Dana classification | 64.1b.1.1 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | R3m |
| Unit cell | a = 14.04, c = 60.6 [Å]; Z = 6 |
| Identification | |
| 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) |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.62, nε = 1.63 (approximated) |
| Pleochroism | Colorless to pink (W), pink (E) |
| Ultraviolet fluorescence | Orange-red |
| Common impurities | Sr, REE, K, Ba, Zr |
| References | [2][3] |
Alluaivite is a rare mineral of the eudialyte group,[3] with complex formula written as Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O.[4][3] 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.[5][6] Alluaivite is named after Mt. Alluaiv in Lovozero Tundry massif, Kola Peninsula, Russia, where it is found in ultra-agpaitic, hyperalkaline pegmatites.[2][3][4]
