metamorphic
Lapis Lazuli
Lapis lazuli (Mainly Lazurite: Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5-5.5 (Mohs); Color: Deep blue with gold pyrite flecks and white calcite streaks; Lustre: Dull to vitreous; Crystal Structure: Isometric (for constituent minerals); Specific Gravity: 2.7-2.9
- Hardness
- 5-5
- Color
- Deep blue with gold pyrite flecks and white calcite streaks
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Physical properties
Hardness: 5-5.5 (Mohs); Color: Deep blue with gold pyrite flecks and white calcite streaks; Lustre: Dull to vitreous; Crystal Structure: Isometric (for constituent minerals); Specific Gravity: 2.7-2.9
Formation & geological history
Formed through contact metamorphism where heat and pressure from intrusive igneous rocks transform limestone or dolostone. Most deposits are found in marble-rich geological environments.
Uses & applications
Highly valued as a gemstone for jewelry, ornamental carvings, and historically used to create ultramarine pigment for fine arts and cosmetics.
Geological facts
Lapis lazuli has been mined for over 6,500 years. It was used in the burial mask of Tutankhamun and was prized by ancient Egyptians, Sumerians, and Romans.
Field identification & locations
Identify by its characteristic intense royal blue color and the presence of metallic yellow pyrite inclusions. It leaves a light blue streak on a porcelain plate and emits a rotten-egg smell when touched by acid.
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