How to identify Smoky Quartz

To correctly identify Smoky Quartz (SiO2 (Smoky Quartz variety)), 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 light brownish-gray to dark brown, often with a smoky appearance. Can be almost black (Morion). The color is typically uniform but can be zoned.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) on crystal faces and conchoidal fracture surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly rough on crystal faces; conchoidal fracture surfaces are very smooth.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Typically forms in hexagonal prisms terminated by rhombohedral faces. Can also be massive or granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in igneous rocks (especially granites, pegmatites, and rhyolites), metamorphic rocks (gneisses, schists), and hydrothermal veins. Often associated with other quartz varieties, feldspars, and micas.

Key Facts

Hardness

7 on the Mohs scale.

Specific Gravity

2.65 g/cm3.

Crystal System

Trigonal.

Color

Brownish-gray to black.

Luster

Vitreous.

Transparency

Transparent to opaque.

Fracture

Conchoidal.

Cleavage

None.

Composition

Silicon dioxide (SiO2).

Physical characteristics

• Crystal Habit: Prismatic, often with hexagonal cross-section, terminated by rhombohedral faces. Also massive, granular.
• Cleavage Type: None.
• Fracture Type: Conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous.

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