How to identify Quartzite

To correctly identify Quartzite (Quartzite), 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, yellow, green, or blue due to impurities (e.g., iron oxides for red/pink, chlorite for green).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to sugary on freshly broken surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granoblastic, interlocking mosaic of quartz crystals. Original clastic texture of sandstone is usually obliterated. Can be fine-grained to coarse-grained.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Anhedral, interlocking grains of quartz.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No true cleavage; exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Forms in regions of regional metamorphism (e.g., mountain belts) or contact metamorphism where quartz-rich sandstones are subjected to high temperatures and pressures. Often found in association with other metamorphic rocks like schist, gneiss, and marble.

Key Facts

Hardness

7 on the Mohs scale

Specific Gravity

2.65 g/cm³

Crystal System

Trigonal (for quartz component)

Color

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

Luster

Vitreous (glassy) to sugary

Transparency

Translucent to opaque

Fracture

Conchoidal to subconchoidal

Cleavage

None (poor parting may occur along relict bedding planes)

Composition

Primarily quartz (SiO2), typically >90%.

Physical characteristics

• Crystal Habit: Granoblastic, interlocking mosaic of anhedral quartz grains.
• Cleavage Type: None; breaks by fracture.
• Fracture Type: Conchoidal to subconchoidal, producing sharp edges.
• Tenacity: Brittle, but extremely tough due to interlocking grains.
• Luster Type: Vitreous (glassy) on fresh surfaces, can appear sugary.

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