Alluaivite

 Alluaivite (IMA symbol: Aav[3]) is a rare mineral of the eudialyte group,[2] with complex formula written as Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O.[4][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.[5][6] Alluaivite is named after Mt. Alluaiv in Lovozero Tundry massif, Kola Peninsula, Russia, where it is found in ultra-agpaitic, hyperalkaline pegmatites.[1][2][4]

Alluaivite [Aav]
General
CategorySilicate mineral, Cyclosilicate
Formula
(repeating unit)		Na19(Ca,Mn)6(Ti,Nb)3Si26O74Cl·2H2O
Strunz classification9.CO.10 (10 ed)
8/E.25-40 (8 ed)
Dana classification64.1b.1.1
Crystal systemTrigonal
Crystal classHexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space groupR3m
Unit cella = 14.04, c = 60.6 [Å]; Z = 6
Identification
ColorColorless to weak brownish pink
Crystal habitirregular accumulations
CleavageNone
FractureConchoidal
TenacityBrittle
Mohs scale hardness5-6
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density2.76 (measured)
Optical propertiesUniaxial (+)
Refractive indexnω=1.62, nε=1.63 (approximated)
PleochroismColorless to pink (W), pink (E)
Ultraviolet fluorescenceOrange-red
Common impuritiesSr, REE, K, Ba, Zr
References[1][2]

Notes on chemistryEdit

Alluaivite contains relatively high amounts of admixing strontium, cerium, potassium, and barium, with lesser amounts of substituting lanthanum and zirconium.[1]

Occurrence and associationEdit

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]

 

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
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Note

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License.