Holmquistite defines a series of orthorhombic Group 1 amphiboles whose compositions can be expressed as AQBLi2 C[(Mg,Fe2+)3(Al, Fe3+)2] TSi8O22(OH)2. Holmquistites are rather rare amphiboles, and generally occur at the contact between lithium-rich pegmatites and country rocks; their formation has always been ascribed to metasomatism around highly fractionated lithium-rich pegmatites that intrude amphibolites.
This rare mineral comes from Western Australia.
Group: Lithium Amphibole
Crystal System: Orthorhombic
Colour: Black, dark violet, sky blue
Streak: White with blue tinge
Hardness: 5 1/2