How to identify Blue Quartz

To correctly identify Blue Quartz (Quartz (SiO2) with inclusions of fibrous minerals like crocidolite or tourmaline), 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

   Shades of blue, from pale sky blue to deep indigo, often mottled or streaky due to inclusions. Can be grayish-blue or violet-blue.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to greasy on fractured surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or crystalline. May show fibrous textures internally due to inclusions.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually occurs as massive aggregates or as inclusions within larger quartz crystals. Well-formed hexagonal prisms with pyramidal terminations are possible if the quartz grew unimpeded.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None (conchoidal fracture is characteristic of quartz).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in metamorphic rocks (e.g., schists, gneisses), hydrothermal veins, pegmatites, and sometimes in igneous rocks. The specific environment depends on the type of fibrous inclusion.

Key Facts

Hardness

7 (Mohs scale)

Specific Gravity

2.65 - 2.66 g/cm³

Crystal System

Trigonal

Color

Blue, grayish-blue, violet-blue (due to inclusions)

Luster

Vitreous to greasy

Transparency

Translucent to opaque

Fracture

Conchoidal

Cleavage

None

Composition

Silicon dioxide (SiO2) with fibrous mineral inclusions (e.g., crocidolite, dumortierite, tourmaline)

Physical characteristics

• Crystal Habit: Massive, granular, prismatic crystals (less common for the blue variety itself, more for the host quartz)
• Cleavage Type: None
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) to greasy

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