metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White to light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under extreme heat and pressure, typically during mountain-building events. Geological age varies by location, often Proterozoic to Paleozoic.
Uses & applications
Used in construction as crushed stone for road beds, in the chemical industry as a source of silica, and as decorative stone in architecture and landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it resists erosion much better than the surrounding rock.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid. Commonly found in metamorphic terrains worldwide and as rounded pebbles in riverbeds or beaches.
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