How to identify Quartzite

To correctly identify Quartzite (Metamorphic rock composed primarily of quartz), 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 red/pink, chlorite for green).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to greasy on freshly broken surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granular, sugary, or saccharoidal. The interlocking quartz grains are typically visible, but individual sand grains are not easily distinguished. Non-foliated.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Anhedral, interlocking mosaic of quartz crystals.

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

   Formed in regions of regional metamorphism associated with mountain building (orogenic belts) or in contact metamorphic aureoles around large igneous intrusions. Often found in ancient cratonic areas and mountain ranges.

Key Facts

Hardness

7 on the Mohs scale

Specific Gravity

2.65 g/cm³

Crystal System

Trigonal (for individual quartz crystals)

Color

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

Luster

Vitreous to greasy

Transparency

Translucent to opaque

Fracture

Conchoidal to subconchoidal

Cleavage

None (though individual quartz crystals may show poor rhombohedral parting)

Composition

Primarily quartz (SiO2), typically >90%.

Physical characteristics

• Crystal Habit: Anhedral, interlocking granular mosaic
• Cleavage Type: None
• Fracture Type: Conchoidal to subconchoidal
• Tenacity: Brittle, extremely tough
• Luster Type: Vitreous (glassy) to greasy

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