metamorphic
Lapis Lazuli
Complex mixture of minerals (lazurite, calcite, pyrite, and sodalite); (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2
Hardness: 5.0-5.5 (Mohs); Color: Deep celestial blue to violet-blue; Luster: Vitreous to greasy; Crystal Structure: Isometric (for lazurite component); Cleavage: Poor; Specific Gravity: 2.7 to 2.9
- Hardness
- 5
- Color
- Deep celestial blue to violet-blue
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5.0-5.5 (Mohs); Color: Deep celestial blue to violet-blue; Luster: Vitreous to greasy; Crystal Structure: Isometric (for lazurite component); Cleavage: Poor; Specific Gravity: 2.7 to 2.9
Formation & geological history
Formed via contact metamorphism, where limestone or dolomite are altered by hydrothermal activity. Notable deposits in Afghanistan (Sar-e-Sang) date back over 6,000 years, found in marble and skarn environments.
Uses & applications
Used primarily in jewelry (cabochons, beads), decorative carvings, and inlay work. Historically ground into the expensive 'ultramarine' pigment for Renaissance painters.
Geological facts
Lapis lazuli were among the most prized stones in Ancient Egypt and Mesopotamia; the funeral mask of Tutankhamun features lapis inlays. Unlike most gemstones, it is a rock (a combination of minerals) rather than a single mineral species.
Field identification & locations
Identify in the field by its intense blue color, the presence of golden flecks (pyrite), and white streaks (calcite). It is commonly found in Afghanistan, Chile (Andes), Russia (Lake Baikal), and the USA (California/Colorado).
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