How to identify Quartz and Garnet

To correctly identify Quartz and Garnet (Quartz (SiO2) and Garnet Group), 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: Colorless, white, gray, purple (amethyst), yellow (citrine), pink (rose quartz), brown (smoky quartz), black (morion). Garnet: Typically red, reddish-brown, orange, yellow, green, black. Rarely blue.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Quartz: Vitreous to greasy. Garnet: Vitreous to resinous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Quartz: Crystalline, granular, massive. Garnet: Granular, euhedral to subhedral crystals embedded in a matrix.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz: Hexagonal prisms with pyramidal terminations, massive, cryptocrystalline. Garnet: Dodecahedral, trapezohedral, or granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz: None (conchoidal fracture). Garnet: None (conchoidal to uneven fracture).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphic rocks (schists, gneisses, amphibolites), igneous rocks (granites, pegmatites), sedimentary rocks (as detrital grains in sandstones, conglomerates), and placer deposits.

Key Facts

Hardness

Quartz: 7 (Mohs). Garnet: 6.5-7.5 (Mohs).

Specific Gravity

Quartz: 2.65. Garnet: 3.5-4.3 (varies with composition).

Crystal System

Quartz: Trigonal. Garnet: Isometric.

Color

Quartz: Colorless, white, purple, pink, yellow, brown, black. Garnet: Red, orange, yellow, green, brown, black.

Luster

Quartz: Vitreous to greasy. Garnet: Vitreous to resinous.

Transparency

Transparent to translucent to opaque (for both).

Fracture

Quartz: Conchoidal. Garnet: Conchoidal to uneven.

Cleavage

Quartz: None. Garnet: None.

Composition

Quartz: Silicon dioxide (SiO2). Garnet: Complex silicates (X3Y2(SiO4)3).

Physical characteristics

• Crystal Habit: Quartz: Prismatic, massive, granular, cryptocrystalline. Garnet: Dodecahedral, trapezohedral, granular.
• Cleavage Type: Quartz: Absent. Garnet: Absent.
• Fracture Type: Quartz: Conchoidal. Garnet: Conchoidal to uneven.
• Tenacity: Quartz: Brittle. Garnet: Brittle.
• Luster Type: Quartz: Vitreous to greasy. Garnet: Vitreous to resinous.

Explore Quartz and Garnet