metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or brownish; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal) system in microstructure; Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or brownish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, white, or brownish; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal) system in microstructure; Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the sand grains to recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as decorative stone in architecture, countertops, and flooring.
Geological facts
Quartzite is so tough that it often breaks through the original quartz sand grains rather than around them, which is a key distinction from sandstone. It is highly resistant to chemical weathering.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel nail) and grainy but crystalline texture. Found globally in mountainous regions where tectonic activity occurs.
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