White crystals of the very rare K-Al borosilicate mineral kalborsite from the TL in Khibiny area in Russia (Khibiny Massif, Murmansk Oblast, Russian Federation) in a dark contrasting matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Kalborsite
Kalborsite is an IMA-recognized mineral species in the silicate class, with the chemical formula K₆Al₄BSi₆O₂₀(OH)₄Cl.
It crystallizes in the tetragonal crystal system (space group P-42_1c). It is a member of the Edingtonite structural group.
Key properties: Mohs hardness 6; specific gravity 2.5; Vitreous to pearly on cleavages luster; optically uniaxial.
IMA symbol Kbs, IMA status: approved, named in 1979.
Forms rims around lovozerite in segregations of pectolite, in rischorrite pegmatite from a differentiated alkalic massif.
It is found associated with Pectolite, lovozerite.
The name refers to potassium, KALium, BORate, and SIlicon in the composition.