metamorphic
Lapis Lazuli
Lapis Lazuli (A metamorphic rock primarily composed of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, along with Calcite and Pyrite)
Hardness: 5 to 5.5 Mohs. Color: Deep azure blue to violet-blue, often with gold-colored specks (pyrite) and white marbling (calcite). Luster: Vitreous to greasy. Crystal structure: Aggregate/Granular. Cleavage: None (fracture is uneven). Specific Gravity: 2.7 to 2.9.
- Hardness
- 5 to 5
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5 to 5.5 Mohs. Color: Deep azure blue to violet-blue, often with gold-colored specks (pyrite) and white marbling (calcite). Luster: Vitreous to greasy. Crystal structure: Aggregate/Granular. Cleavage: None (fracture is uneven). Specific Gravity: 2.7 to 2.9.
Formation & geological history
Formed through contact metamorphism, where heat from intruding magma transforms limestone or dolomite into a silicate-rich rock. Primary source deposits in Afghanistan have been mined for over 6,000 years.
Uses & applications
Predominantly used as a gemstone for jewelry (cabochons, beads), decorative carvings, and historical pigments (ultramarine). It is also highly valued by mineral collectors and used in metaphysical practices.
Geological facts
Ancient Egyptians used lapis lazuli for the funeral mask of Tutankhamun and feared it as a symbol of the night sky. In the Renaissance, it was ground into the most expensive pigment available, used by Michelangelo and Vermeer.
Field identification & locations
Identify by its intense 'ultramarine' blue color, blue streak (when ground), and the presence of brassy pyrite inclusions. Commonly found in Afghanistan (Sar-i Sang), Russia (Lake Baikal), Chile, and Myanmar. To test authenticity, check for coolness to the touch and the absence of dye leaching when wiped with acetone.
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