Chemical Formula: (Mg,Fe2+)Al2(PO4)2(OH)2
Locality: Werfen, Salzburg, Austria
Name Origin: From the Arabic azul – “sky” and the Greek lithos – “stone.”
Lazulite ((Mg,Fe2+)Al2(PO4)2(OH)2) is a blue, phosphate mineral containing magnesium, iron, and aluminium phosphate. Lazulite forms one endmember of a solid solution series with the darker iron rich scorzalite.
Lazulite crystallizes in the monoclinic system. Crystal habits include steep bipyramidal or wedge-shaped crystals. Lazulite has a Mohs hardness of 5.5 to 6 and a specific gravity of 3.0 to 3.1. It is infusible and insoluble.
Discovery date : 1795
Optical and misc. Properties : Subtranslucent to opaque
Refractive Index : from 1,61 to 1,64
Axial angle 2V: 69°
Color: Blue, Blue green, Light blue, Black blue.
Density: 3 – 3.1, Average = 3.05
Diaphaneity: Subtranslucent to opaque
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 5-6 – Between Apatite and Orthoclase
Luster: Vitreous (Glassy)