Brownish banalsite from the famous Langban deposit (Långban, Filipstad, Värmland County, Sweden) on matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Banalsite
A rare barium-sodium feldspar-group tectosilicate that forms a complete solid solution with its strontium counterpart stronalsite.
Intro adapted from Wikipedia (CC BY-SA).
Banalsite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂BaAl₄Si₄O₁₆.
It crystallizes in the orthorhombic crystal system (space group Ibam).
Key properties: Mohs hardness 6.5; specific gravity 3.065; Vitreous, pearly on cleavage luster; refractive index 1.573; optically biaxial.
IMA symbol Bns, grandfathered status — known before the IMA’s founding, named in 1944.
Found in veinlets through manganese ore and in lenses in metamorphosed mudstone (Benallt mine, Wales). From altered ultramafic xenoliths in alkaline rocks (nepheline syenite, jacupirangite).
It is found associated with Calcite, natrolite, tephroite, jacobsite, alleghanyite, pyrophanite, Mn-rich biotite, andradite, harmotome, apatite (Benallt mine, Wales); magnetoplumbite.
Derived from the chemical symbols for the major constituents, Ba, Na, Al, Si.