metamorphic
Lapis Lazuli (polished cabochon)
Lazurite-rich metamorphic rock (approx. Na6Ca2Al6Si6O24(SO4,S,Cl)2)
Hardness: 5-5.5 (Mohs); Color: Deep celestial blue with white calcite and golden pyrite; Luster: Vitreous to greasy; Crystal Structure: Isometric (massive); Cleavage: Poor; Specific Gravity: 2.7-2.9.
- Hardness
- 5-5
- Color
- Deep celestial blue with white calcite and golden pyrite
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5-5.5 (Mohs); Color: Deep celestial blue with white calcite and golden pyrite; Luster: Vitreous to greasy; Crystal Structure: Isometric (massive); Cleavage: Poor; Specific Gravity: 2.7-2.9.
Formation & geological history
Formed via contact metamorphism when limestone or marble is altered by heat and chemical activity from nearby magma; typically occurring in Precambrian to tertiary formations depending on local geology.
Uses & applications
Predominantly used for jewelry, lapidary carvings, and high-end architectural inlay; historically ground into powder to create 'ultramarine' pigment for fine art.
Geological facts
Lapis lazuli was highly prized by Ancient Egyptians for amulets and funeral masks, most famously found in Tutankhamun’s burial mask. It is a rock, not a mineral, because it is composed of multiple minerals.
Field identification & locations
Identify in the field by its intense blue color and characteristic brassy-gold flecks of pyrite. Major sources include the Sar-e-Sang mines in Afghanistan, as well as locations in Chile, Russia, and the USA.
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