metamorphic
Lapis Lazuli
Lapis lazuli (a rock primarily composed of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5-5.5 (Mohs scale); Color: Deep blue with gold-flecked pyrite or white calcite streaks; Luster: Vitreous to dull; Crystal structure: Isometric (Lazurite component); Specific gravity: 2.7-2.9
- Hardness
- 5-5
- Color
- Deep blue with gold-flecked pyrite or white calcite streaks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Deep blue with gold-flecked pyrite or white calcite streaks; Luster: Vitreous to dull; Crystal structure: Isometric (Lazurite component); Specific gravity: 2.7-2.9
Formation & geological history
Formed through contact metamorphism where limestone or dolomite is altered by hydrothermal processes. Famous deposits are over 6,000 years old, particularly those in the Sar-e-Sang mines of Afghanistan.
Uses & applications
Used primarily in jewelry, ornamental carvings, and as a pigment (ultramarine). Historically used for the funeral mask of Tutankhamun and Renaissance paintings.
Geological facts
The 'gold' specks found in high-quality lapis are actually inclusions of pyrite (fool's gold). It is one of the first gemstones used by human civilizations, dating back to the Neolithic period.
Field identification & locations
Identify by its unique 'royal blue' color, often accompanied by gold pyrite specks. Look for it in mountainous regions where limestone has been subject to heat. It is mostly found in Afghanistan, Chile, and Russia.
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