Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
This refers to an association where the mineral lazurite is found within or alongside quartz. Lazurite is a tectosilicate mineral, a member of the sodalite group, characterized by its vivid blue to violet-blue color. It often occurs as disseminated grains or masses within a matrix. Quartz, a silicate mineral, is typically colorless, white, or translucent, and is much harder than lazurite. When found together, the quartz can appear as clear or milky inclusions, veins, or as the host rock for the lazurite. The most famous manifestation of this association is Lapis Lazuli, which is a rock composed primarily of lazurite, calcite, and often pyrite, but can also contain minor quartz, diopside, and other silicates.
How to Identify
- Color
- Lazurite: Intense azure blue, violet-blue, greenish-blue. Quartz: Colorless, white, milky, or translucent, sometimes smoky or amethystine.
- Luster
- Lazurite: Vitreous to greasy. Quartz: Vitreous.
- Texture
- Lazurite: Granular, massive. Quartz: Crystalline, massive, sometimes sugary.
- Crystal Form
- Lazurite: Typically massive, granular, or as dodecahedral crystals (rare). Quartz: Prismatic crystals with pyramidal terminations, massive, granular.
- Cleavage
- Lazurite: Imperfect to distinct on {110}. Quartz: None (conchoidal fracture).
- Geological Environment
- Contact metamorphic zones, especially in metamorphosed impure limestones or dolomites (skarns), often associated with granitic intrusions. Quartz can be primary in the protolith or introduced by hydrothermal fluids during metamorphism.
Key Facts
- Hardness: Lazurite: 5-5.5 (Mohs); Quartz: 7 (Mohs)
- Specific Gravity: Lazurite: 2.38-2.42; Quartz: 2.65
- Crystal System: Lazurite: Isometric; Quartz: Trigonal
- Color: Lazurite: Deep azure blue, violet-blue, greenish-blue; Quartz: Colorless, white, milky, various other colors
- Luster: Lazurite: Vitreous to greasy; Quartz: Vitreous
- Transparency: Lazurite: Translucent to opaque; Quartz: Transparent to translucent
- Fracture: Lazurite: Uneven; Quartz: Conchoidal
- Cleavage: Lazurite: Imperfect to distinct on {110}; Quartz: None
- Composition: Lazurite: Sodium calcium aluminum silicate with sulfur, sulfate, and chloride; Quartz: Silicon dioxide
Quick Check
- Color: Vivid blue (lazurite) with colorless/white/translucent (quartz)
- Luster: Vitreous to greasy (lazurite), Vitreous (quartz)
- Streak: Light blue (lazurite), White (quartz)
Physical Characteristics
- Crystal Habit: Lazurite: Massive, granular, disseminated grains, rare dodecahedral crystals; Quartz: Prismatic crystals, massive, granular, cryptocrystalline
- Cleavage Type: Lazurite: Imperfect to distinct in two directions; Quartz: Absent
- Fracture Type: Lazurite: Uneven; Quartz: Conchoidal
- Tenacity: Lazurite: Brittle; Quartz: Brittle
- Luster Type: Lazurite: Vitreous to greasy; Quartz: Vitreous
Formation
Lazurite, the primary blue component, forms through contact metamorphism of impure limestones or dolomites. This process involves metasomatism, where fluids rich in sulfur, chlorine, and sodium react with carbonate rocks containing aluminum and silicon. Quartz (SiO2) is a ubiquitous mineral and can be present in the protolith or introduced during metamorphism. The association of quartz with lazurite typically occurs when the metamorphic fluids interact with siliceous carbonate rocks, or when quartz veins cut through or are intergrown with lazurite-bearing skarns.
Usage
The primary use of material containing lazurite, especially Lapis Lazuli, is as a gemstone and ornamental stone. It has been prized for millennia for its intense blue color, used in jewelry, carvings, and as a pigment (ultramarine). Quartz, when associated, can enhance the durability of the material for carving or provide a contrasting matrix. Pure lazurite is rarely found in large enough quantities for industrial use beyond its ornamental value.
Age Distribution
Varies widely depending on the geological setting of metamorphism, ranging from Precambrian to Cenozoic.
Where to Find
Sar-e-Sang, Badakhshan Province, Afghanistan
The most historically significant and primary source of high-quality Lapis Lazuli (lazurite-rich rock), mined for over 6,000 years. Here, lazurite occurs in crystalline marble, often with pyrite and calcite, and sometimes minor quartz.
Lake Baikal region, Siberia, Russia
Another important source of lazurite, found in metamorphosed carbonate rocks.
Ovalle, Coquimbo Region, Chile
Produces lazurite, often associated with calcite and other silicates, in metamorphic settings.
Baffin Island, Nunavut, Canada
Known for occurrences of lazurite in metamorphic rocks.
Finding Tips
Geological Context
Focus on areas known for contact metamorphism of carbonate rocks, particularly near granitic intrusions. Skarn deposits are prime targets.
Associated Minerals
Look for calcite (white, softer than quartz), pyrite (metallic gold flecks), diopside (greenish-white), and other silicates often found with lazurite.
Color and Luster
The intense blue color of lazurite is distinctive. Quartz will appear as clearer or milky areas contrasting with the blue. Lazurite has a vitreous to greasy luster, while quartz is distinctly vitreous.
Hardness Test
Lazurite (5-5.5) is softer than quartz (7). A steel knife can scratch lazurite but not quartz. This helps differentiate the two components within a sample.
Similar Rocks
Sodalite
Na4Al3Si3O12Cl
Also known as: Blue Sodalite
Azurite
Cu3(CO3)2(OH)2
Also known as: Chessylite
Dumortierite
Al7(BO3)(SiO4)3O3
Also known as: Blue Quartz (when included)
Howlite (dyed blue)
Ca2B5SiO9(OH)5
Also known as: Turquenite (when dyed)
Scientific Classification
- Mineral Class
- Tectosilicate (Lazurite), Tectosilicate (Quartz)
- Group
- Sodalite Group (Lazurite), Quartz Group (Quartz)
- Crystal System
- Isometric (Lazurite), Trigonal (Quartz)
- Chemical Formula
- (Na,Ca)8[(S,SO4,Cl)2|(Al6Si6O24)] (Lazurite), SiO2 (Quartz)
- Composition
- Sodium calcium aluminum silicate with sulfur, sulfate, and chloride (Lazurite), Silicon dioxide (Quartz)
Explore Lapis Lazuli (rock) or Lazurite in Quartz
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.