metamorphic
Lapis Lazuli
Lazurite-rich metamorphic rock (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2
Hardness: 5 to 5.5 Mohs scale; Color: Deep blue with gold-flecked pyrite and white calcite inclusions; Luster: Vitreous to greasy; Crystal Structure: Isometric (lazurite component); Specific Gravity: 2.7 to 2.9
- Hardness
- 5 to 5
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5 to 5.5 Mohs scale; Color: Deep blue with gold-flecked pyrite and white calcite inclusions; Luster: Vitreous to greasy; Crystal Structure: Isometric (lazurite component); Specific Gravity: 2.7 to 2.9
Formation & geological history
Formed via contact metamorphism of limestone or marble. Major deposits in Afghanistan date back over 6,000 years, primarily found in tectonic subduction zones.
Uses & applications
Used extensively in jewelry, ornamental carvings, and historically as the pigment 'ultramarine' for fine art. Also valued as a collector's specimen.
Geological facts
Lapis lazuli was used in the funeral mask of Tutankhamun and was the primary source of the world's most expensive blue pigment until the 19th century.
Field identification & locations
Identify by its characteristic intense royal blue color and the presence of metallic yellow pyrite specks. Found primarily in Afghanistan, Chile, Russia, and Canada. Look for a 'rotten egg' smell when scratched or treated with acid due to sulfur content.
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