lazurite

noun

1. a mineral, sodium aluminum silicate and sulfide, Na5Al3Si3O12S3, occurring in deep-blue crystals, used for ornamental purposes.

noun

1. a rare blue mineral consisting of a sodium–calcium–aluminium silicate and sulphide: used as the gemstone lapis lazuli. Formula: (Na,Ca) 8 (AlSiO 4) 6 (SO 4,S,Cl) 2