metamorphic
Lapis Lazuli
Lazurite-rich metamorphic rock ((Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5-5.5 Mohs scale; Color: Deep royal blue with gold pyrite flecks and white calcite veins; Luster: Dull to vitreous; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.7–2.9
- Hardness
- 5-5
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5-5.5 Mohs scale; Color: Deep royal blue with gold pyrite flecks and white calcite veins; Luster: Dull to vitreous; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.7–2.9
Formation & geological history
Formed through contact metamorphism where limestone or marble is altered by hydrothermal processes. Major deposits are found in ancient crystalline limestone formations over 60 million years old.
Uses & applications
Used primarily in jewelry (cabochons, beads), decorative carvings, ornaments, and historically ground into ultramarine pigment for fine art.
Geological facts
Lapis lazuli was highly prized by ancient Egyptians, who used it for the funeral mask of Tutankhamun. It is technically a rock, not a mineral, because it is composed of multiple minerals including lazurite, pyrite, and calcite.
Field identification & locations
Identifiable by its intense blue color and characteristic metallic pyrite ('gold') inclusions. Found prominently in the Sar-e-Sang mines of Afghanistan, as well as Chile, Russia, and the USA. Collectors look for high lazurite content with minimal white calcite.
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