How to identify Tourmalinated Quartz

To correctly identify Tourmalinated Quartz (Quartz with Tourmaline inclusions), 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 can be colorless, white, gray, or smoky brown. Tourmaline inclusions are typically black (schorl), but can rarely be other colors if different tourmaline species are present.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) for quartz; vitreous to resinous for tourmaline.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly uneven fracture surfaces for quartz; tourmaline inclusions are typically prismatic and can be felt if exposed on the surface.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz typically forms hexagonal prisms with pyramidal terminations. Tourmaline inclusions are usually acicular (needle-like) or prismatic, often oriented randomly or in parallel bundles within the quartz.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz: None. Tourmaline: Poor prismatic cleavage, rarely observed in inclusions.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, and greisens associated with granitic intrusions. Often found in metamorphic rocks that have undergone metasomatism.

Key Facts

Hardness

7 (Mohs for quartz); 7-7.5 (Mohs for tourmaline)

Specific Gravity

2.65 (for quartz); 3.0-3.2 (for schorl tourmaline)

Crystal System

Trigonal (for quartz); Trigonal (for tourmaline)

Color

Colorless, white, gray, or smoky quartz with black (most common), green, or pink tourmaline inclusions.

Luster

Vitreous

Transparency

Transparent to translucent (quartz); Opaque (tourmaline inclusions)

Fracture

Conchoidal (quartz); Uneven to conchoidal (tourmaline)

Cleavage

None (quartz); Poor prismatic (tourmaline)

Composition

SiO2 (quartz) with complex borosilicate inclusions (tourmaline group minerals, e.g., Na(Fe2+)_3Al_6(BO_3)_3Si_6O_18(OH)_4 for schorl)

Physical characteristics

• Crystal Habit: Quartz: Prismatic, often terminated. Tourmaline: Acicular, prismatic, often embedded.
• Cleavage Type: Quartz: None. Tourmaline: Poor prismatic {1120}.
• Fracture Type: Conchoidal (quartz); Uneven to conchoidal (tourmaline).
• Tenacity: Brittle.
• Luster Type: Vitreous.

Explore Tourmalinated Quartz