How to identify Blue Quartz

To correctly identify Blue Quartz (Quartz (SiO2) with inclusions of fibrous minerals like Magnesioriebeckite 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

   Ranges from pale, milky blue to deep, vibrant blue. The color is often unevenly distributed and can appear streaky or patchy due to the fibrous inclusions.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to greasy on fractured surfaces. Can exhibit a subtle chatoyancy or aventurescence when polished due to oriented inclusions.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or crystalline. The presence of fibrous inclusions can sometimes give it a slightly silky appearance, especially in areas where the fibers are concentrated.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually occurs as massive aggregates, granular masses, or as inclusions within larger quartz crystals. Well-formed macroscopic crystals are rare for the blue variety itself, though the host quartz may exhibit typical hexagonal prismatic forms.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Quartz lacks cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in various geological settings, including hydrothermal veins, pegmatites, and regionally metamorphosed rocks. The specific environment depends on the formation conditions of the included fibrous minerals. For instance, dumortierite-bearing blue quartz is often associated with aluminum-rich metamorphic rocks or pegmatites, while magnesioriebeckite-bearing blue quartz can be found in alkali-rich metamorphic or igneous rocks.

Key Facts

Hardness

7 (Mohs scale)

Specific Gravity

2.65 - 2.66 g/cm³

Crystal System

Trigonal

Color

Blue, due to fibrous mineral inclusions (e.g., magnesioriebeckite, dumortierite, tourmaline)

Luster

Vitreous to greasy

Transparency

Translucent to opaque

Fracture

Conchoidal

Cleavage

None

Composition

Silicon dioxide (SiO2) with various fibrous mineral inclusions

Physical characteristics

• Crystal Habit: Typically massive, granular, or as inclusions within larger quartz crystals. Macroscopic crystals of blue quartz are rare.
• Cleavage Type: Absent
• Fracture Type: Conchoidal, uneven
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) to greasy

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