Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Lapis Lazuli is a deep-blue metamorphic rock composed primarily of lazurite (25-40%), along with varying amounts of calcite (white), pyrite (metallic yellow), and sodalite (greyish-blue). Its characteristic intense blue color is due to the presence of the polysulfide radical (S3-) within the lazurite crystal structure. The quality of Lapis Lazuli is determined by the intensity and uniformity of its blue color, the absence of excessive calcite, and the presence of finely disseminated pyrite flecks, which are often considered desirable.
How to Identify
- Color
- Intense, uniform deep blue to violet-blue. Often contains golden flecks of pyrite and white streaks or patches of calcite.
- Luster
- Dull to greasy, sometimes vitreous on fresh fracture surfaces.
- Texture
- Fine-grained to medium-grained, granular, often with visible inclusions of pyrite and calcite.
- Crystal Form
- As a rock, it does not exhibit a single crystal form. The constituent mineral lazurite forms dodecahedral crystals, but these are rarely visible in the massive rock.
- Cleavage
- No distinct cleavage as a rock. Lazurite itself has imperfect dodecahedral cleavage, but this is not typically observed in the massive rock.
- Geological Environment
- Contact metamorphic zones, particularly in metamorphosed limestones or marbles, often near igneous intrusions.
Key Facts
- Hardness: 5 to 6 (Mohs scale)
- Specific Gravity: 2.7 to 2.9 g/cm³
- Crystal System: Cubic (for lazurite, the primary mineral component)
- Color: Intense blue, violet-blue, greenish-blue
- Luster: Dull, greasy, sometimes vitreous
- Transparency: Opaque
- Fracture: Uneven to conchoidal
- Cleavage: None (as a rock); imperfect dodecahedral (for lazurite)
- Composition: A rock composed primarily of lazurite, calcite, pyrite, and sodalite.
Quick Check
- Color: Deep blue with golden pyrite flecks and white calcite streaks.
- Luster: Dull to greasy.
- Streak: Light blue (for lazurite component).
Physical Characteristics
- Crystal Habit: Massive, granular (for the rock); dodecahedral (for individual lazurite crystals, rarely observed)
- 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) with sulfur-rich fluids, often associated with granitic intrusions. The primary blue mineral, lazurite, forms when sulfur, chlorine, and hydroxyl groups are incorporated into the sodalite structure under specific temperature and pressure conditions. The presence of pyrite (golden flecks) and calcite (white streaks) are common accessory minerals.
Usage
Historically and currently used as a gemstone, ornamental stone, and pigment (ultramarine). It has been highly prized since antiquity for jewelry, carvings, inlays, and as a cosmetic. Ultramarine pigment, derived from ground lapis lazuli, was historically one of the most expensive and sought-after blue pigments.
Age Distribution
Typically found in Precambrian to Paleozoic metamorphic terrains, though specific deposits can vary.
Where to Find
Badakhshan Province, Afghanistan
The most significant and historically important source, producing the finest quality Lapis Lazuli for over 6,000 years. Occurs in marble xenoliths within granitic intrusions.
Lake Baikal, Siberia, Russia
Another important source, producing high-quality material, often with a slightly different hue and less pyrite than Afghan material.
Ovalle, Coquimbo Region, Chile
Produces a lighter blue Lapis Lazuli, often with more prominent white calcite veining. Discovered in the early 20th century.
Baffin Island, Nunavut, Canada
More recent discoveries, producing material of varying quality.
Colorado, USA
Minor occurrences, typically not of gem quality, but of geological interest.
Finding Tips
Geological Context
Focus on areas with contact metamorphic zones, especially where limestone or marble has been intruded by granitic rocks. Look for skarn-like environments.
Associated Minerals
Lapis Lazuli is almost always found with calcite (white), pyrite (golden metallic), and sometimes sodalite (greyish-blue). The presence of these minerals can be an indicator.
Color and Luster
Look for the characteristic intense blue color. Freshly broken surfaces may show a dull to greasy luster. The blue color is often more vibrant when wet.
Hardness Test
Lapis Lazuli has a Mohs hardness of 5 to 6. It can be scratched by a steel file but will scratch glass. This helps differentiate it from softer minerals.
Acid Test (Caution)
A small drop of dilute hydrochloric acid (HCl) will cause a slight effervescence (fizzing) on the calcite inclusions within Lapis Lazuli, and may release a faint odor of hydrogen sulfide (rotten egg smell) due to the sulfur in lazurite. Use extreme caution and proper ventilation if performing this test.
Similar Rocks
Sodalite
Sodalite
Also known as: Blue Sodalite
Dumortierite
Dumortierite
Also known as: Blue Quartz
Azurite
Azurite
Also known as: Chessylite
Howlite (dyed blue)
Howlite
Also known as: Turquenite (when dyed)
Scientific Classification
- Mineral Class
- Tectosilicate (for lazurite, a feldspathoid mineral)
- Group
- Sodalite Group (for lazurite)
- Crystal System
- Cubic (for lazurite)
- Chemical Formula
- (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)] (for lazurite, the main component)
- Composition
- A rock consisting of lazurite (sodium calcium aluminum silicate sulfate), calcite (calcium carbonate), pyrite (iron sulfide), and sodalite (sodium aluminum silicate chloride).
Explore Lapis Lazuli
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.