Lapis Lazuli
Image: James St. John (CC BY 2.0)
Mineral NameLapis Lazuli
Chemical Formula(Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)] (primarily lazurite, a component mineral)
Mohs Hardness5
Crystal Systemcubic
Lustervitreous
Streak Colorlight blue
Cleavageimperfect (for lazurite, generally absent in the rock)
Fractureuneven to conchoidal
Specific Gravity2.7
Colorsdeep blue, white, golden
Transparencyopaque
Type LocalitySar-e-Sang Deposit, Hindu-Kush Mountains, Afghanistan
Mineral GroupMetamorphic Rock (composed primarily of lazurite, a tectosilicate)
Usesjewelry, ornamental objects, pigment (ultramarine)
Associated Mineralslazurite, calcite, pyrite
Rarityuncommon
Description
A deep blue metamorphic rock, often characterized by its intense blue color, white calcite veins, and golden pyrite flecks. The image shows a deep blue specimen with visible whitish inclusions and brassy gold specks.
Geological Context
Lapis lazuli is a lazuritic metamorphite, formed by contact metamorphism of limestone in the presence of sulfur-rich fluids. The specimen is from the Precambrian Sakhi Formation in Afghanistan.
