How to identify Blue Quartz

To correctly identify Blue Quartz (Quartz (SiO2) with inclusions of various blue minerals (e.g., dumortierite, tourmaline, or magnesioriebeckite)), 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

   Ranges from pale, milky blue to deep, intense blue. The color is often unevenly distributed due to the nature of the inclusions. Can appear grayish-blue or violet-blue depending on the specific inclusions.

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. The texture can sometimes appear slightly fibrous or speckled due to the inclusions.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually occurs as massive aggregates, but can also be found as well-formed hexagonal prisms with pyramidal terminations, characteristic of quartz. Inclusions are often oriented along the growth directions of the quartz.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Quartz exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in a variety of geological settings including pegmatites, hydrothermal veins, metamorphic rocks (especially those rich in aluminum or boron for dumortierite), and sometimes in granitic intrusions. The presence of specific blue minerals dictates the precise environment.

Key Facts

Hardness

7 (Mohs scale)

Specific Gravity

2.65 - 2.66 g/cm³ (consistent with pure quartz)

Crystal System

Trigonal

Color

Blue (due to inclusions)

Luster

Vitreous to greasy

Transparency

Translucent to opaque, rarely transparent

Fracture

Conchoidal

Cleavage

None

Composition

SiO2 (Quartz) with inclusions of blue minerals such as dumortierite, magnesioriebeckite, or blue tourmaline.

Physical characteristics

• Crystal Habit: Massive, granular, prismatic crystals (hexagonal prisms with pyramidal terminations).
• Cleavage Type: None
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) to greasy

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