| Banalsite | |
| Category: | Tectosilicate |
| Formula: | BaNa2Al4Si4O16 |
| Imasymbol: | Bns[1] |
| Strunz: | 9.FA.60 |
| System: | Orthorhombic |
| Class: | Pyramidal (mm2) H-M symbol: (mm2) |
| Symmetry: | Iba2 |
| Unit Cell: | a = 8.496(2) Å, b = 9.983(2) Å, c = 16.755(3) Å; Z = 4 |
| Color: | White |
| Habit: | Rarely showing traces of crystal faces; coarsely crystalline to compact, massive |
| Cleavage: | Good on and |
| Mohs: | 6.5 |
| Luster: | Vitreous, pearly on cleavage |
| Streak: | White |
| Diaphaneity: | Translucent to transparent |
| Gravity: | 3.065 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.570 nβ = 1.571 nγ = 1.578 |
| 2V: | Measured: 41°, Calculated: 52° |
| References: | [2] [3] [4] [5] |
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.[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]