metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white/grey; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none (fractures conchoidally); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white/grey
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white/grey; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none (fractures conchoidally); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogenesis).
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative building stone or countertop material.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and hills because it resists weathering better than surrounding rocks.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sugary, crystalline texture. It is found in mountain ranges globally where ancient sea beds have been uplifted.
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