lapis lazuli

الوصف

he main component of lapis lazuli is lazurite (*5% to *0%), a feldspathoid silicate minerals with the formula (Na,Ca)8(AlSiO4)6(S,SO4,Cl)**2.[5] Most lapis lazuli also contains calcite (white),sodalite (blue), and pyrite (metallic yellow). Other possible constituents: augite; diopside;enstatite; mica; hauynite; hornblende, and nosean. Some lapis lazuli contains trace amounts of the sulfur-rich löllingite variety geyerite.

Lapis lazuli usually occurs in crystalline marble as a result of.contact metamorphism.
Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments, and vases. It was also ground and processed to make the pigment ultramarine for tempera paint and, more rarely, oil paint. Its usage as a pigment in oil paint ended in the early *9th century when a chemically identical synthetic variety, often called French ultramarine, became available.