How to identify Tourmalinated Quartz

To correctly identify Tourmalinated Quartz (Quartz (SiO2) with Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)), 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 black.

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 conchoidal fracture for quartz; tourmaline inclusions are typically prismatic and can feel slightly rough if exposed.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz often forms hexagonal prisms with pyramidal terminations; tourmaline forms elongated prismatic crystals, often with striations parallel to the c-axis.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz has no true cleavage, exhibiting conchoidal fracture. Tourmaline has poor prismatic cleavage, rarely observed.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, and granitic rocks.

Key Facts

Hardness

Quartz: 7 on Mohs scale; Tourmaline: 7-7.5 on Mohs scale.

Specific Gravity

Quartz: 2.65 g/cm³; Schorl: 3.18-3.22 g/cm³ (overall aggregate will be between these values, closer to quartz if tourmaline is sparse).

Crystal System

Quartz: Trigonal; Tourmaline: Trigonal.

Color

Colorless, white, or smoky quartz with black tourmaline inclusions.

Luster

Vitreous.

Transparency

Quartz: Transparent to translucent; Tourmaline: Opaque.

Fracture

Conchoidal (quartz); uneven to conchoidal (tourmaline).

Cleavage

None (quartz); poor prismatic (tourmaline).

Composition

Silicon dioxide (SiO2) for quartz; complex borosilicate for schorl (NaFe3Al6(BO3)3Si6O18(OH)4).

Physical characteristics

• Crystal Habit: Quartz: Prismatic, massive, granular; Tourmaline: Prismatic, acicular, columnar, radiating.
• Cleavage Type: Quartz: None; Tourmaline: Poor prismatic {1120}.
• Fracture Type: Quartz: Conchoidal; Tourmaline: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous.

Explore Tourmalinated Quartz