Chemical composition -- A compound of sodium, calcium, aluminum, silicon, oxygen, and sulfur, usually found as a rock mixture of lazurite, calcite, and pyrite.
Color --Blue to violet-blue.
Optics -- R.I. 1.50.
Durability -- Hardness 5-6.
Crystal structure -- Isometric (cubic). Crystals are very rare and tiny. Usually found as massive material mixed with pyrite and calcite.
Specific Gravity -- 2.38-2.9, depending on presence of calcite and pyrite.
Sources -- The best source is in the mountains of Afghanistan, where the mines have been dug for the past 7,000 years! Poorer quality material is found in Chile and other locations. Lapis occurs in huge sizes and has been widely used for ornamental and architectural items as well as for jewelry.