metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: gray, white, or yellowish; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Color
- gray, white, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: gray, white, or yellowish; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together into a dense, interlocking matrix.
Uses & applications
Used as a decorative stone in construction, flooring, roofing tiles, and railroad ballast. Due to its hardness, it is also used in the manufacturing of abrasive materials.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of ridges and mountains. It is harder than steel.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its 'sugary' texture on a fresh break. Unlike sandstone, quartzite breaks through the sand grains rather than around them.
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