The name "blue stone" comes from the Arabic-Latin. Since Lapislazuli rarely occurs purely, it can almost be described as rock. Freed pyrite on the lapis is desirable and is seen as evidence of ist authenticity. The colour can be improved by low heating.

LAPISLAZULI (Lapis, Lasurstein)
Colour: lasurblau, violet, greenish-blue
Mohs hardness: 5.0-6.0
Density: 2.5-3.0
Transparency: inscrutable
Break: meek, grainy