Banalsite

Banalsite
General
CategoryTectosilicate
Formula
(repeating unit)		BaNa2Al4Si4O16
IMA symbolBns[1]
Strunz classification9.FA.60
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
H-M symbol: (mm2)
Space groupIba2
Unit cella = 8.496(2) Å,
b = 9.983(2) Å,
c = 16.755(3) Å; Z = 4
Identification
ColorWhite
Crystal habitRarely showing traces of crystal faces; coarsely crystalline to compact, massive
CleavageGood on {110} and {001}
Mohs scale hardness6.5
LusterVitreous, pearly on cleavage
StreakWhite
DiaphaneityTranslucent to transparent
Specific gravity3.065
Optical propertiesBiaxial (+)
Refractive indexnα = 1.570 nβ = 1.571 nγ = 1.578
2V angleMeasured: 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]

  1. ^ 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.
  2. ^ Mineralienatlas
  3. ^ a b http://rruff.geo.arizona.edu/doclib/hom/banalsite.pdf Handbook of Mineralogy
  4. ^ a b http://www.mindat.org/min-504.html Mindat.org
  5. ^ http://www.webmineral.com/data/Banalsite.shtml Webmineral data
  6. ^ 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)
  7. ^ 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)