Alluaivite
Alluaivite is a rare mineral of the eudialyte group,[2] with complex formula written as Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O.[3][2] 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.[4][5] Alluaivite is named after Mt. Alluaiv in Lovozero Tundry massif, Kola Peninsula, Russia, where it is found in ultra-agpaitic, hyperalkaline pegmatites.[1][2][3]
Alluaivite | |
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General | |
Category | Silicate mineral, Cyclosilicate |
Formula (repeating unit) | Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O |
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 | [1][2] |
Notes on chemistry
Alluaivite contains relatively high amounts of admixing strontium, cerium, potassium, and barium, with lesser amounts of substituting lanthanum and zirconium.[1]
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.[1]
References
- http://www.handbookofmineralogy.org/pdfs/Alluaivite.PDF Handbook of Mineralogy
- http://www.mindat.org/show.php?id=141&ld=2 Mindat
- Khomyakov A. P., Netschelyustov G. N. and Rastsvetaeva R. K. 1990: Alluaivite Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl.2H2O - A new titanosilicate mineral of eudialyte-like structure. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 119(3), 117-120, in Jambor J. L. and Puziewicz J. 1991: New mineral names. American Mineralogist, 76, 1728-1735;
- Khomyakov, A.P., Nechelyustov, G.N., and Rastsvetaeva, R.K., 2006. Labyrinthite (Na,K,Sr)35Ca12Fe3Zr6TiSi51O144(O,OH,H2O)9Cl3, a new mineral with a modular eudialyte-like structure from Khibiny Alkaline Massif, Kola Peninsula, Russia. Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva 135(2), 38-49
- Khomyakov, A.P., Nechelyustov, G.N., and Rastsvetaeva, R.K., 2009: Dualite, Na30(Ca,Na,Ce,Sr)12(Na,Mn,Fe,Ti)6Zr3Ti3MnSi51O144(OH,H2O,Cl)9, a new zircono-titanosilicate with a modular eudialyte-like structure from the Lovozero alkaline Pluton, Kola Peninsula, Russia. Geology of Ore Deposits 50(7), 574-582