(Na,Ca)4(Al,SiO4)3(SO4,S,Cl). A brilliant, opaque, azure-blue colour gemstone, with a hardness on the Mhos scale of 5.5. Lapis lazuli is a mixture of minerals, primarily containing the lazurite (blue) with small amounts of calcite, sodalite, and gold-coloured flecks of pyrite. Lazurite is a sodium, calcium, aluminium sulpho-chlorosilicate. The blue coloration, which can be deep or pale, greenish or nearly purple, is produced by sulphur contained in the lazurite. Lapis lazuli has been commercially mined since 3000 BCE at the Badakhshan mines in Afghanistan. Other mines are found in Argentina, Siberia, Chile, Myanmar (formerly Burma), Pakistan and California. The semiprecious blue stone was, and still is, used for jewellery, mosaics and small carvings. Lapis lazuli was also ground and purified to make natural ultramarine blue pigments. Synonyms: lazurite; lapis; Persian blue; Fra Angelico Blue; Armenian stone; ultramarine blue (pigment). Museum of Fine Arts, Boston (2000); Trench (2000).[J. Cassar, R. de Angelis]