How to identify Tourmalinated Quartz

To correctly identify Tourmalinated Quartz (Schorl in 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

   Quartz matrix is typically colorless, white, or smoky. Tourmaline inclusions are invariably black (schorl).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) for both quartz and tourmaline.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly uneven fracture surfaces. The embedded tourmaline crystals provide a distinct visual texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz typically forms hexagonal prisms with pyramidal terminations, though it can be massive. Schorl forms prismatic, often striated, crystals, which can be acicular, columnar, or blocky within the quartz.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz has no true cleavage, exhibiting conchoidal fracture. Schorl has indistinct cleavage parallel to the prism faces.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Pegmatites, hydrothermal veins, and regionally metamorphosed rocks. Often found in granitic intrusions and associated contact metamorphic zones.

Key Facts

Hardness

Quartz: 7 on Mohs scale. Schorl: 7-7.5 on Mohs scale.

Specific Gravity

Quartz: 2.65 g/cm³. Schorl: 3.06-3.26 g/cm³.

Crystal System

Quartz: Trigonal. Schorl: Trigonal.

Color

Colorless to smoky (quartz), black (schorl).

Luster

Vitreous.

Transparency

Transparent to translucent (quartz), opaque (schorl).

Fracture

Conchoidal (quartz), uneven to conchoidal (schorl).

Cleavage

None (quartz), indistinct (schorl).

Composition

Quartz: SiO₂. Schorl: Na(Fe²⁺)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄.

Physical characteristics

• Crystal Habit: Quartz: Prismatic, massive. Schorl: Prismatic, acicular, columnar, radiating.
• Cleavage Type: Quartz: None. Schorl: Indistinct on {1120} and {1011}.
• Fracture Type: Conchoidal (quartz), uneven to conchoidal (schorl).
• Tenacity: Brittle.
• Luster Type: Vitreous.

Explore Tourmalinated Quartz