lazurite

noun

1. (uncountable, usually)A mineral of metamorphosed limestones. Lazurite forms the gemstone lapis lazuli, and crushed lazurite provided the ultramarine color in artists' paint of the Old Masters. Sodalite and lazurite form the sodalite group of silicate minerals. Chemical composition: Sodium aluminum silicate with sulphur, Na₄₋₅Al₃Si₃O₁₂S.

   “Although there are dozens of different types of gems, among the best known and most important are […] . (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)”