metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to yellowish-gray; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6–2.7
- Hardness
- 7 on Mohs scale
- Color
- White to yellowish-gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to yellowish-gray; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6–2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize into a dense interlocking mosaic.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction, in the manufacture of glass and ceramics, and as a durable material for countertops.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the caps of ridges and mountains. It is significantly harder and more durable than the sandstone from which it originated.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, granular texture. Unlike marble, it will not fizz with acid. Common in orogenic belts and precambrian shields.
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