Bearthite
Bearthite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₂Al(PO₄)₂(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Brackebuschite structural group.
Key properties: Mohs hardness 5; specific gravity 3.25; White streak; optically biaxial.
IMA symbol Bth, IMA status: approved, named in 1986.
Found in synmetamorphic quartz segregations and as an accessory mineral in high-pressure metamorphic rocks.
It is found associated with Lazulite, apatite, kyanite, coesite, pyrope, paragonite, muscovite, almandine, rutile, augelite, wardite, goyazite, hydroxylherderite, quartz, albite, talc.
The mineral was named to honor Professor Peter Bearth (1902–1989), for his pioneering petrologic studies of the high-pressure terranes of the western Alps.