metamorphic
Lapis Lazuli
Lapis Lazuli (Aggregate of Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Pyrite, and Calcite)
Hardness: 5 to 5.5 (Mohs scale); Color: Deep celestial blue to violet-blue; Luster: Dull to greasy (vitreous when polished); Crystal Structure: Isometric (aggregate); Cleavage: None; Specific Gravity: 2.7 to 2.9.
- Hardness
- 5 to 5
- Color
- Deep celestial blue to violet-blue
- Luster
- Dull to greasy (vitreous when polished)
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Physical properties
Hardness: 5 to 5.5 (Mohs scale); Color: Deep celestial blue to violet-blue; Luster: Dull to greasy (vitreous when polished); Crystal Structure: Isometric (aggregate); Cleavage: None; Specific Gravity: 2.7 to 2.9.
Formation & geological history
Formed through contact metamorphism where heat and pressure from intrusive igneous rocks transform limestones or dolomites. Major deposits date back over 6,000 years in the Sar-e-Sang mines of Afghanistan.
Uses & applications
Primarily used in jewelry for cabochons, beads, and carvings. Historically ground into 'Ultramarine' pigment for fine arts. Also used in high-end ornamental inlay and interior decor.
Geological facts
Lapis lazuli has been used since the Neolithic period; it was a favorite of Egyptian pharaohs for amulets and funeral masks, most notably the mask of Tutankhamun. The name is derived from Latin 'Lapis' (stone) and Persian 'Lāzhward' (blue).
Field identification & locations
Identify by its characteristic intense blue color peppered with golden specks (Pyrite) and white mottling (Calcite). Found primarily in Afghanistan, Chile, Russia, and Canada. Collectors look for 'ultramarine' color with minimal white calcite.
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