metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, or pink; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown, tan, or pink
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, or pink; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during tectonic plate collisions and mountain-building events.
Uses & applications
Used extensively in road construction, railway ballast, building stone, and decorative landscaping. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so hard that it will scratch glass and even steel. It is more resistant to weathering than the sandstone from which it originated, often forming the caps of ridges and mountains.
Field identification & locations
Identify in the field by its grainy, sandpaper-like texture that does not rub off, and its inability to be scratched by a steel knife. Commonly found in folded mountain belts globally.
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