Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Lapis Lazuli is a beautiful, intense blue metamorphic rock composed predominantly of the mineral lazurite (25-40%), along with varying amounts of calcite (white), pyrite (metallic yellow), and minor constituents like sodalite, hauyne, and wollastonite. Its distinctive deep blue color, often speckled with golden pyrite and streaked with white calcite, makes it highly recognizable and valued.
How to Identify
- Color
- Intense azure blue to violet-blue, often with golden flecks of pyrite and white streaks of calcite.
- Luster
- Dull to greasy, sometimes vitreous on polished surfaces.
- Texture
- Fine-grained to medium-grained, compact.
- Crystal Form
- Massive, granular aggregates. Individual lazurite crystals are rare and typically dodecahedral.
- Cleavage
- None (as a rock). Lazurite itself has imperfect cleavage on {110}.
- Geological Environment
- Contact metamorphic zones, particularly in metamorphosed limestones or marbles, often associated with granitic intrusions.
Key Facts
- Hardness: 5 to 6 on the Mohs scale (due to varying mineral composition).
- Specific Gravity: 2.7 to 2.9 g/cm³.
- Crystal System: Isometric (for lazurite, the primary mineral). The rock itself is massive.
- Color: Intense azure blue to violet-blue.
- Luster: Dull to greasy.
- Transparency: Opaque.
- Fracture: Uneven to conchoidal.
- Cleavage: None (as a rock).
- Composition: Rock composed primarily of lazurite (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)], calcite (CaCO3), and pyrite (FeS2).
Quick Check
- Color: Deep blue with golden pyrite flecks and white calcite streaks.
- Luster: Dull to greasy.
- Streak: Light blue.
Physical Characteristics
- Crystal Habit: Massive, granular aggregates.
- Cleavage Type: None (as a rock).
- Fracture Type: Uneven to conchoidal.
- Tenacity: Brittle.
- Luster Type: Dull to greasy.
Formation
Lapis Lazuli forms through contact metamorphism of calcareous rocks (limestone or marble) in the presence of sulfur-rich fluids. The primary mineral, lazurite, is a feldspathoid that develops under specific high-temperature, low-pressure conditions. The blue color is due to the presence of polysulfide ions within the lazurite structure. Calcite provides the white streaks, and pyrite forms the characteristic golden flecks.
Usage
Historically and currently used as a gemstone, ornamental stone, and pigment (ultramarine blue). It was highly prized in ancient civilizations for jewelry, carvings, and decorative objects. Ultramarine pigment, derived from ground lapis lazuli, was one of the most expensive and sought-after blue pigments until the 19th century.
Age Distribution
Formed during regional or contact metamorphism, often associated with ancient geological events, with deposits ranging from Precambrian to Cenozoic.
Where to Find
Sar-e-Sang, Badakhshan Province, Afghanistan
The most significant and historically important source, producing the finest quality Lapis Lazuli for over 6,000 years. Occurs in marble lenses within metamorphic terrains.
Lake Baikal, Siberia, Russia
Another important source, found in similar metamorphic settings.
Ovalle, Coquimbo Region, Chile
Produces a lighter blue, often with more calcite, found in metamorphic rocks.
Colorado, USA
Minor occurrences, typically in metamorphic rocks associated with igneous intrusions.
Finding Tips
Look for Metamorphic Zones
Focus on areas with contact metamorphism, especially where limestone or marble has been intruded by igneous rocks.
Identify Associated Minerals
Search for blue minerals in association with white calcite and metallic yellow pyrite. The presence of these minerals together is a strong indicator.
Check for Color and Luster
The distinctive deep blue color and dull to greasy luster are key identifiers. Be wary of imitations.
Similar Rocks
Sodalite
Na4Al3Si3O12Cl
Also known as: Blue Sodalite
Dumortierite
Al7(BO3)(SiO4)3O3
Also known as: Blue Quartz
Scientific Classification
- Mineral Class
- Tectosilicate (for lazurite, a feldspathoid)
- Group
- Sodalite Group (for lazurite)
- Crystal System
- Isometric (for lazurite)
- Chemical Formula
- Rock, primarily (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)] (lazurite) + CaCO3 (calcite) + FeS2 (pyrite)
- Composition
- Sodium calcium alumino-silicate with sulfur, chlorine, and sulfate, mixed with calcium carbonate and iron sulfide.
Explore Lapis Lazuli
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.