metamorphic
Lapis Lazuli
Lapis lazuli (Complex silicate rock containing Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Calcite, and Pyrite)
Hardness: 5-5.5 Mohs; Color: Ultramarine blue with white calcite streaks and gold pyrite flecks; Luster: Dull to vitreous; Crystal structure: Harmonic isometric (aggregates); Specific gravity: 2.7-2.9
- Hardness
- 5-5
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5-5.5 Mohs; Color: Ultramarine blue with white calcite streaks and gold pyrite flecks; Luster: Dull to vitreous; Crystal structure: Harmonic isometric (aggregates); Specific gravity: 2.7-2.9
Formation & geological history
Formed through contact metamorphism, where limestone or marble is altered by heat and chemical changes from nearby igneous intrusions. Most famous deposits are over 6,000 years old in Afghanistan.
Uses & applications
Used primarily in jewelry, ornamental carvings, beads, and historically ground into 'ultramarine' pigment for fine art painting.
Geological facts
Lapis was highly prized by Ancient Egyptians for amulets and funerary masks, including Tutankhamun's mask. It is a rock, not a mineral, because it is composed of multiple minerals.
Field identification & locations
Identify by its intense 'Royal Blue' color, the presence of 'fool's gold' (pyrite) inclusions, and a distinctive sulfur-like smell when ground or scratched. Main sources include Afghanistan, Chile, and Russia.
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