metamorphic
Lapis Lazuli
Lapis lazuli (primary mineral: Lazurite, (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5 to 5.5 on Mohs scale; Color: Intense deep blue (lazurite), often with gold flecks (pyrite) and white streaks (calcite); Luster: Vitreous to greasy; Crystal Structure: Isometric (as lazurite); Cleavage: None; 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 on Mohs scale; Color: Intense deep blue (lazurite), often with gold flecks (pyrite) and white streaks (calcite); Luster: Vitreous to greasy; Crystal Structure: Isometric (as lazurite); Cleavage: None; Specific Gravity: 2.7 to 2.9
Formation & geological history
Formed through contact metamorphism where limestone or marble is altered by hydrothermal processes. It typically occurs in crystalline limestones. The most famous deposits in Afghanistan are over 6,000 years old.
Uses & applications
Used primarily for jewelry, decorative carvings, and ornamental objects. Historically ground into powder to create the expensive pigment 'ultramarine' for Renaissance paintings.
Geological facts
Lapis lazuli has been mined in the Sar-e-Sang mines of Afghanistan for over 7,000 years. It was highly prized by Ancient Egyptians, who used it for the funeral mask of Tutankhamun.
Field identification & locations
Identify by its unique 'royal blue' color accompanied by golden pyrite inclusions. Unlike sodalite, lapis usually contains these metallic gold specks and lacks transparency. Found primarily in Afghanistan, Chile, Russia, and Canada.
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