How to identify Lapis Lazuli (rock) or Lazurite in Quartz

To correctly identify Lapis Lazuli (rock) or Lazurite in Quartz (SiO2 with (Na,Ca)8[(S,SO4,Cl)2|(Al6Si6O24)]), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Lazurite: Intense azure blue, violet-blue, greenish-blue. Quartz: Colorless, white, milky, or translucent, sometimes smoky or amethystine.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Lazurite: Vitreous to greasy. Quartz: Vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Lazurite: Granular, massive. Quartz: Crystalline, massive, sometimes sugary.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Lazurite: Typically massive, granular, or as dodecahedral crystals (rare). Quartz: Prismatic crystals with pyramidal terminations, massive, granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Lazurite: Imperfect to distinct on {110}. Quartz: None (conchoidal fracture).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   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

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

Explore Lapis Lazuli (rock) or Lazurite in Quartz