Mineral Na8[(Si,A1)6O24](S,SO4) belonging to the sodalite group of minerals and with a similar composition to haüyne and nosean; sp. gr. 2.3–2.4; hardness 5.5; cubic; intense, deep, azure-blue, violet, light blue, or greenish-blue; vitreous lustre; usually compact, massive; cleavage imperfect, rhombododecahedral; occurs in the contact zone of alkaline, igneous rocks, in association with carbonate rocks, and in alkaline lavas. The variety lapis lazuli is used to make ornaments.
Subjects: Earth Sciences and Geography.