metamorphic
Lapis Lazuli
Lapis Lazuli (Rock composed primarily of Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Calcite, and Pyrite)
Hardness: 5.0-5.5 (Mohs scale); Color: Deep celestial blue to violet-blue; Luster: Dull to vitreous; Crystal Structure: Isometric (lazurite grains); Specific Gravity: 2.7 to 2.9. Characterized by white calcite streaks and gold-colored pyrite inclusions.
- Hardness
- 5
- Color
- Deep celestial blue to violet-blue
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5.0-5.5 (Mohs scale); Color: Deep celestial blue to violet-blue; Luster: Dull to vitreous; Crystal Structure: Isometric (lazurite grains); Specific Gravity: 2.7 to 2.9. Characterized by white calcite streaks and gold-colored pyrite inclusions.
Formation & geological history
Formed through the contact metamorphism of limestone or marble by granitic or syenitic intrusions. The process replaces the carbonate minerals with complex silicates. Found in locations dating back thousands of years, typically in high-altitude terrain.
Uses & applications
Used primarily in jewelry (beads, cabochons), carvings, and ornaments. Historically ground into powder to create 'ultramarine' pigment for fine arts and cosmetics.
Geological facts
Lapis lazuli was one of the most highly prized substances in ancient Egypt and Mesopotamia. It is a rock, not a mineral, because it is composed of several different mineral species rather than just one.
Field identification & locations
Identify by its intense blue color, presence of golden-metallic pyrite flecks, and light-colored calcite. Commonly found in Afghanistan (Sar-e-Sang), Chile, Russia (Lake Baikal), and Myanmar. Collectors should check for dye by rubbing with acetone to ensure it is natural.
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