metamorphic
Lapis Lazuli
Lapis Lazuli (Complex silicate mixture including Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5-5.5; Color: Deep blue with gold-flecked Pyrite and white Calcite; Luster: Vitreous to greasy; Crystal Structure: Isometric (Lazurite part); Cleavage: Poor; Specific Gravity: 2.7-2.9
- Hardness
- 5-5
- Color
- Deep blue with gold-flecked Pyrite and white Calcite
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5-5.5; Color: Deep blue with gold-flecked Pyrite and white Calcite; Luster: Vitreous to greasy; Crystal Structure: Isometric (Lazurite part); Cleavage: Poor; Specific Gravity: 2.7-2.9
Formation & geological history
Formed through contact metamorphism where limestone or marble is altered by hydrothermal activity. Often found in mountain ranges such as the Hindu Kush, dating back millions of years.
Uses & applications
Used primarily in jewelry, lapidary arts, and ornamental carvings. Historically ground to create the pigment 'ultramarine' for fine art painting.
Geological facts
It has been mined for over 6,000 years; the most famous source is the Sar-e-Sang mines in Afghanistan. King Tutankhamun's funeral mask is heavily inlaid with Lapis Lazuli.
Field identification & locations
Identify by its intense 'royal blue' color and the presence of metallic gold Pyrite inclusions. High-grade specimens lack white Calcite streaks and have uniform color and fine grain.
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