Lapis lazuli is completely opaque and often contains small gold or silver pyrite inclusions that run through the material in veins or layers. The best quality lapis lazuli is intense dark blue, with minor patches of white calcite and brassy yellow pyrite. The coloring agent of lapis lazuli is sulfur. It is relatively rare and commonly forms in crystalline limestones as a product of contact metamorphism. The luster of lapis lazuli is vitreous to greasy.
Lapis lazuli was used as a gemstone by ancient Egyptians; the mask of Tutankhamun, for example, has lapis lazuli inlays. Powdered lapis lazuli was also used as a cosmetic, as a pigment, and as medicine. Ancient Greeks and Romans believed that sapphires, probably lapis lazuli, cured eye diseases and set prisoners free. Another ancient belief was that it protected the wearer from the evil eye; probably because the color blue flecked with gold pyrite resembles the night sky, the dwelling place of God. Ancient Buddhists believed that lapis lazuli brought peace of mind and equanimity, and was good for dispelling evil thoughts.
Lapis lazuli is found in Afghanistan, Argentina, Canada, Chile, Myanmar (formerly Burma), Russia (Siberia), United States (Colorado, California).
Lapis lazuli is often confused with azurite, dumortierite, dyed howlite, lazulite, sodalite, and glass imitations.