Banalsite is a rare barium, sodium aluminium silicate mineral with formula: BaNa2Al4Si4O16. Banalsite is a tectosilicate of the feldspar group.
| Banalsite | |
|---|---|
| General | |
| Category | Tectosilicate |
| Formula (repeating unit) | BaNa2Al4Si4O16 |
| IMA symbol | Bns[1] |
| Strunz classification | 9.FA.60 |
| Crystal system | Orthorhombic |
| Crystal class | Pyramidal (mm2) H-M symbol: (mm2) |
| Space group | Iba2 |
| Unit cell | a = 8.496(2) Å, b = 9.983(2) Å, c = 16.755(3) Å; Z = 4 |
| Identification | |
| Color | White |
| Crystal habit | Rarely showing traces of crystal faces; coarsely crystalline to compact, massive |
| Cleavage | Good on {110} and {001} |
| Mohs scale hardness | 6.5 |
| Luster | Vitreous, pearly on cleavage |
| Streak | White |
| Diaphaneity | Translucent to transparent |
| Specific gravity | 3.065 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.570 nβ = 1.571 nγ = 1.578 |
| 2V angle | Measured: 41°, Calculated: 52° |
| References | [2][3][4][5] |
Banalsite and its strontium analogue, stronalsite (SrNa2Al4Si4O16), constitute a complete solid solution series.[6] In addition limited solid solution with calcium exists between these and lisetite: CaNa2Al4Si4O16.[7]
It was first described in 1944 for an occurrence in the Benallt Mine, Rhiw, Llanfaelrhys, Lleyn Peninsula, Gwynedd (Caernarvonshire), Wales.[4] The name is derived from the chemical symbols of its composition. It has also been reported from Långban, Värmland, Sweden and from the Kalahari manganese field, Cape Province, South Africa.[3] It has recently been reported from the nepheline syenites of the Zhidoy massif, Eastern Sayan, Siberia, Russia; the Prairie Lake complex of alkaline rocks and carbonatites, Superior Alkaline Province, northwestern Ontario, Canada; the Pilansberg peralkaline complex, South Africa; the Sakharjok alkaline complex in the Kola Alkaline Province, Kola Peninsula of northwestern Russia (the Gremyakha–Vyrmes peralkaline complex, and the Turiy Mys complex of ultramafic–alkaline rocks and carbonatites).[7]
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.
- ^ Mineralienatlas
- ^ a b http://rruff.geo.arizona.edu/doclib/hom/banalsite.pdf Handbook of Mineralogy
- ^ a b http://www.mindat.org/min-504.html Mindat.org
- ^ http://www.webmineral.com/data/Banalsite.shtml Webmineral data
- ^ Liferovich, Ruslan P., et al., The Crystal Structure of Stronalsite and a Redetermination of the Structure of Banalsite, The Canadian Mineralogist, Vol. 44, pp. 533-546 (2006)
- ^ a b Liferovich, Ruslan P., et al., Paragenesis and Composition of Banalsite, Stronalsite, and Their Solid Solution in Nepheline Syenite and Ultramafic Alkaline Rocks, The Canadian Mineralogist, Vol. 44, pp. 929-942 (2006)
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