How to identify Quartzite

To correctly identify Quartzite (Metamorphic rock (recrystallized quartz sandstone)), 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

   Typically white to light gray, but can be pink, red, purple, yellow, green, or blue due to impurities (e.g., iron oxides for reds/pinks, chlorite for greens).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to greasy on fresh surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granoblastic (interlocking, equigranular crystals), nonfoliated. Original clastic texture of sandstone is usually obliterated. Grain size is typically medium to coarse-grained.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Anhedral (lacking well-formed crystal faces) interlocking quartz grains.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No true cleavage; exhibits conchoidal to splintery fracture. The original quartz grains themselves have poor to indistinct cleavage, but the interlocking nature of quartzite prevents macroscopic cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Formed in regions of regional metamorphism associated with convergent plate boundaries (mountain belts) or by contact metamorphism adjacent to large igneous intrusions. Often found in ancient cratonic areas and uplifted metamorphic terrains.

Key Facts

Hardness

7 (Mohs scale)

Specific Gravity

2.65 g/cm³

Crystal System

Trigonal (for quartz mineral)

Color

White, gray, pink, red, purple, yellow, green, blue

Luster

Vitreous to greasy

Transparency

Translucent to opaque

Fracture

Conchoidal to splintery

Cleavage

None (breaks across grains)

Composition

Primarily quartz (SiO2), typically >90% quartz. Minor accessory minerals may include feldspar, mica, garnet, zircon, rutile, magnetite, and iron oxides.

Physical characteristics

• Crystal Habit: Granoblastic, interlocking mosaic of anhedral quartz crystals.
• Cleavage Type: Absent (no true cleavage in the rock; quartz mineral has poor to indistinct cleavage)
• Fracture Type: Conchoidal to splintery
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) to greasy

Explore Quartzite