metamorphic
Lapis Lazuli
Lapis lazuli (complex rock composed of Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Pyrite, and Calcite)
Hardness: 5-5.5 (Mohs); Color: Deep celestial blue with gold pyrite flecks and white calcite streaking; Luster: Vitreous to greasy; Structure: Cubic (lazurite); Cleavage: None; Specific Gravity: 2.7–2.9
- Hardness
- 5-5
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5-5.5 (Mohs); Color: Deep celestial blue with gold pyrite flecks and white calcite streaking; Luster: Vitreous to greasy; Structure: Cubic (lazurite); Cleavage: None; Specific Gravity: 2.7–2.9
Formation & geological history
Formed by contact metamorphism where limestone is altered by heat and pressure. The best specimens have been mined for over 6,000 years in the Sar-e-Sang mines of Afghanistan.
Uses & applications
Used primarily in jewelry (cabochons, beads), decorative carvings, and historical pigments (ultramarine). High-quality specimens are highly sought by mineral collectors.
Geological facts
Historically, it was ground into powder to create 'ultramarine', the most expensive blue pigment available to Renaissance artists like Michelangelo. It was also found in the funeral mask of Tutankhamun.
Field identification & locations
Identify by its intense 'blue-jean' color and the presence of gold-colored pyrite (fools gold) inclusions. Common locations include Afghanistan, Chile, Russia, and Lake Baikal.
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