metamorphic
Lapis Lazuli
Tectosilicate (Na,Ca)8(AlSiO4)6(SO4,S,Cl,OH)2
Hardness: 5-5.5 (Mohs scale); Color: Deep blue with gold flecks (Pyrite) and white veins (Calcite); Luster: Vitreous to greasy; Crystal Structure: Isometric (usually massive); Specific Gravity: 2.7-2.9
- Hardness
- 5-5
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Deep blue with gold flecks (Pyrite) and white veins (Calcite); Luster: Vitreous to greasy; Crystal Structure: Isometric (usually massive); Specific Gravity: 2.7-2.9
Formation & geological history
Formed through contact metamorphism, where heat and pressure from intrusive igneous rocks transform limestone or dolostone. It typically occurs in crystalline marbles.
Uses & applications
Primarily used in jewelry for beads, cabochons, and carvings. Historically ground into 'ultramarine' pigment for fine art and used in ornamental construction like tiles and vases.
Geological facts
The blue color comes from the trisulfur radical anion. It was the favorite stone of ancient Egyptians, including King Tutankhamun, and was used in the famous mask of the pharaoh.
Field identification & locations
Identified by its intense ultramarine blue color and the presence of metallic yellow pyrite inclusions. Found mostly in the Sar-e-Sang mines of Afghanistan, as well as Russia, Chile, and Myanmar.
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