metamorphic
Lapis Lazuli
Lapis Lazuli (Complex metamorphic rock primarily containing Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Hardness: 5-5.5 (Mohs), Color: Deep blue with gold-colored pyrite specks and white calcite veins, Luster: Vitreous to greasy, Crystal structure: Isometric (Lazurite component), Cleavage: Imperfect/None, Specific Gravity: 2.7–2.9
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs), Color: Deep blue with gold-colored pyrite specks and white calcite veins, Luster: Vitreous to greasy, Crystal structure: Isometric (Lazurite component), Cleavage: Imperfect/None, Specific Gravity: 2.7–2.9
Formation & geological history
Formed by contact metamorphism of limestone or marble by granitic or alkaline intrusions. Most famous deposits in Afghanistan date back over 6,000 years, found in ancient metamorphic complexes.
Uses & applications
Used primarily for jewelry (cabochons, beads), decorative carvings, and historically as a pigment (Ultramarine) for Renaissance paintings.
Geological facts
Lapis lazuli was used in the funeral mask of Tutankhamun. It was so highly valued in the Middle Ages and Renaissance that it was more expensive than gold when ground into pigment.
Field identification & locations
Identify by its unique 'royal blue' color, the presence of pyrite 'gold' inclusions, and white calcite streaks. Commonly found in Afghanistan, Chile, Russia, and Lake Baikal.
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