Yellow white crystal aggregates of the very rare Li-mineral bertossaite associated to blue burangaite from the TL for both minerals: Buranga Pegmatite, Gatumba, Ngororero District, Western Province, Rwanda. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Bertossaite
Bertossaite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Li₂CaAl₄(PO₄)₄(OH)₄.
It crystallizes in the orthorhombic crystal system (space group Imcb). It is a member of the Carminite structural group.
Key properties: Mohs hardness 6; specific gravity 3.1; Vitreous luster; optically biaxial.
IMA symbol Bts, IMA status: approved, named in 1965.
Thought to be developed during a late calcium-rich phase of mineralization in a lithium-bearing granite pegmatite.
It is found associated with Amblygonite, lazulite-scorzalite, augelite, brazilianite, apatite, crandallite, trolleite, samuelsonite, quartz.
The mineral was named to honor Antonio Bertossa, Director of the Geological Survey of Rwanda.