How to identify Tourmaline in Quartz with Pyrite

To correctly identify Tourmaline in Quartz with Pyrite (Schorl (Tourmaline Group) in Quartz (SiO2) with Pyrite (FeS2)), 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

   Schorl is typically black, opaque. Quartz is usually colorless, white, or milky, but can be smoky or other colors. Pyrite is brassy yellow, metallic.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Schorl has a vitreous to resinous luster. Quartz has a vitreous luster. Pyrite has a metallic luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   The texture will vary depending on the crystal habits of the individual minerals. Schorl often forms prismatic crystals, quartz can be massive or crystalline, and pyrite can be euhedral or anhedral.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Schorl: Prismatic, often with characteristic rounded triangular cross-section and vertical striations. Quartz: Hexagonal prisms terminating in rhombohedra, or massive/granular. Pyrite: Cubic, pyritohedral, or octahedral crystals, often striated.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Schorl: Indistinct to poor cleavage, typically exhibiting conchoidal to uneven fracture. Quartz: No cleavage, conchoidal fracture. Pyrite: Indistinct cleavage on {001}, typically conchoidal to uneven fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, greisens, and some metamorphic rocks, particularly those associated with granitic intrusions and boron-rich fluids.

Key Facts

Hardness

Schorl: 7-7.5 on Mohs scale. Quartz: 7 on Mohs scale. Pyrite: 6-6.5 on Mohs scale.

Specific Gravity

Schorl: 3.0-3.2. Quartz: 2.65. Pyrite: 4.95-5.10.

Crystal System

Schorl: Trigonal. Quartz: Trigonal. Pyrite: Isometric.

Color

Schorl: Black. Quartz: Colorless, white, smoky. Pyrite: Brassy yellow.

Luster

Schorl: Vitreous to resinous. Quartz: Vitreous. Pyrite: Metallic.

Transparency

Schorl: Opaque. Quartz: Transparent to translucent. Pyrite: Opaque.

Fracture

Schorl: Conchoidal to uneven. Quartz: Conchoidal. Pyrite: Conchoidal to uneven.

Cleavage

Schorl: Indistinct to poor. Quartz: None. Pyrite: Indistinct on {001}.

Composition

Schorl: Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH). Quartz: SiO2. Pyrite: FeS2.

Physical characteristics

• Crystal Habit: Schorl: Prismatic, acicular, massive. Quartz: Prismatic, massive, granular. Pyrite: Cubic, pyritohedral, octahedral, massive.
• Cleavage Type: Schorl: Indistinct. Quartz: None. Pyrite: Indistinct.
• Fracture Type: Schorl: Conchoidal to uneven. Quartz: Conchoidal. Pyrite: Conchoidal to uneven.
• Tenacity: Schorl: Brittle. Quartz: Brittle. Pyrite: Brittle.
• Luster Type: Schorl: Vitreous to resinous. Quartz: Vitreous. Pyrite: Metallic.

Explore Tourmaline in Quartz with Pyrite