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]
| Alluaivite | |
|---|---|
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula (repeating unit) | 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] |
Notes on chemistry
editAlluaivite contains relatively high amounts of admixing strontium, cerium, potassium, and barium, with lesser amounts of substituting lanthanum and zirconium.[2]
Occurrence and association
editAlluaivite 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.[2]
References
edit- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c d http://www.handbookofmineralogy.org/pdfs/Alluaivite.PDF Handbook of Mineralogy
- ^ a b c d http://www.mindat.org/show.php?id=141&ld=2 Mindat
- ^ a b 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; [1]
- ^ 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
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