metamorphic
Lapis Lazuli
Lazurite cluster (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2
Hardness: 5.0-5.5 on Mohs scale; Color: Intense deep blue with golden pyrite inclusions; Luster: Dull to vitreous; Crystal structure: Isometric (usually massive); Specific gravity: 2.7-2.9.
- Hardness
- 5
- Color
- Intense deep blue with golden pyrite inclusions
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5.0-5.5 on Mohs scale; Color: Intense deep blue with golden pyrite inclusions; Luster: Dull to vitreous; Crystal structure: Isometric (usually massive); Specific gravity: 2.7-2.9.
Formation & geological history
Formed through contact metamorphism, typically occurring in crystalline limestones or marble where silica and alumina were present. The world's most famous deposits are over 6,000 years old.
Uses & applications
Primarily used for jewelry, lapidary carvings, decorative ornaments, and historically ground into the pigment 'ultramarine' for fine art.
Geological facts
The blue color comes from the trisulfur radical anion. It was used in the funeral mask of Tutankhamun and was more expensive than gold during the Renaissance.
Field identification & locations
Identified by its distinctive blue streak and the presence of golden pyrite flecks. High-quality specimens are found in the Sar-e-Sang mines of Afghanistan.
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