Banalsite
| Banalsite | |
|---|---|
| General | |
| Category | Tectosilicate |
| Formula (repeating unit) | BaNa2Al4Si4O16 |
| Strunz classification | 09.FA.60 |
| Crystal symmetry | Orthorhombic 2/m 2/m 2/m |
| 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 |
| Crystal system | Orthorhombic |
| 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 | [1][2][3] |
Banalsite is a rare barium, sodium aluminium silicate mineral with formula: BaNa2Al4Si4O16. Banalsite is a tectosilicate of the feldspar group.
Banalsite and its strontium analogue, stronalsite (SrNa2Al4Si4O16), constitute a complete solid solution series.[4] In addition limited solid solution with calcium exists between these and lisetite: CaNa2Al4Si4O16.[5]
It was first described in 1944 for an occurrence in the Benallt Mine, Rhiw, Llanfaelrhys, Lleyn Peninsula, Gwynedd (Caernarvonshire), Wales.[2] 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.[1] 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.[5]
References
- 1 2 http://rruff.geo.arizona.edu/doclib/hom/banalsite.pdf Handbook of Mineralogy
- 1 2 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)
- 1 2 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)