How to identify Smoky Quartz

To correctly identify Smoky Quartz (SiO2 (Smoky Quartz variety of Quartz)), 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 yellowish-brown to dark brown, grayish-brown, or black. 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 as hexagonal prisms terminated by hexagonal pyramids. 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

   Commonly found in granitic pegmatites, hydrothermal veins, alpine-type fissures, and in some metamorphic rocks. It can also occur in alluvial deposits.

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 translucent, rarely opaque

Fracture

Conchoidal

Cleavage

None

Composition

Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Prismatic crystals, often terminated by rhombohedral faces (forming hexagonal pyramids); also massive, granular, or cryptocrystalline.
• Cleavage Type: None
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous (glassy)

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