How to identify Tourmalinated Quartz

To correctly identify Tourmalinated Quartz (Quartz with Schorl (Black 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 host is typically colorless, white, or smoky gray. The tourmaline inclusions are invariably black.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) for the quartz, sub-vitreous to resinous for the tourmaline inclusions.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to conchoidal fracture for quartz; the tourmaline inclusions are typically prismatic and can feel slightly rough if exposed on a broken surface.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz typically forms hexagonal prisms with pyramidal terminations. Schorl forms prismatic, often striated, crystals embedded 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 prismatic cleavage {1120} and {1011}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Pegmatites, hydrothermal veins, and metamorphic rocks where boron-rich fluids interact with silica-rich environments.

Key Facts

Hardness

7 (Mohs for quartz), 7-7.5 (Mohs for schorl)

Specific Gravity

2.65 (for quartz), 3.06-3.20 (for schorl)

Crystal System

Trigonal (for quartz), Trigonal (for schorl)

Color

Colorless, white, or smoky quartz with black inclusions.

Luster

Vitreous (quartz), sub-vitreous to resinous (schorl).

Transparency

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

Fracture

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

Cleavage

None (quartz), indistinct prismatic (schorl).

Composition

SiO₂ (quartz); Na(Fe²⁳)₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH) (schorl)

Physical characteristics

• Crystal Habit: Quartz: Prismatic, often terminated. Schorl: Acicular, prismatic, often striated, embedded within quartz.
• Cleavage Type: Quartz: None. Schorl: Indistinct prismatic.
• Fracture Type: Quartz: Conchoidal. Schorl: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous (quartz), sub-vitreous to resinous (schorl).

Explore Tourmalinated Quartz