How to identify Tourmaline

To correctly identify Tourmaline (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

   Extremely variable, including black (Schorl), pink to red (Rubellite), blue (Indicolite), green (Verdelite), yellow, brown (Dravite), colorless (Achroite), and multi-colored (Watermelon Tourmaline).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to resinous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically smooth crystal faces, often with prominent vertical striations.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Prismatic crystals, often elongated, with a characteristic rounded triangular cross-section. Terminations can be complex, often hemimorphic (different forms at opposite ends of the crystal).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Indistinct to poor basal cleavage, often appearing to lack cleavage. Fracture is more common.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Granitic pegmatites, high-temperature hydrothermal veins, metamorphic schists and gneisses, and less commonly in detrital sediments.

Key Facts

Hardness

7-7.5 on the Mohs scale

Specific Gravity

2.90-3.26 (varies with composition)

Crystal System

Trigonal (hexagonal-rhombohedral)

Color

Extremely variable, often pleochroic

Luster

Vitreous to resinous

Transparency

Transparent to opaque

Fracture

Conchoidal to uneven

Cleavage

Indistinct to poor basal cleavage, often appears to lack cleavage

Composition

Complex borosilicate of aluminum, iron, magnesium, sodium, lithium, and other elements

Physical characteristics

• Crystal Habit: Prismatic, often elongated, acicular, columnar, massive, radiating aggregates. Characteristic rounded triangular cross-section.
• Cleavage Type: Indistinct to poor basal cleavage {0001}, often parting along {1011}.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Vitreous to resinous.

Explore Tourmaline