metamorphic
Quartzite
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Yellowish-tan to white; Luster: Vitreous to dull when weathered; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-tan to white
- Luster
- Vitreous to dull when weathered
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-tan to white; Luster: Vitreous to dull when weathered; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the regional metamorphism of quartzose sandstone. Intense heat and pressure cause the individual quartz grains to recrystallize and fuse together, creating an extremely durable rock.
Uses & applications
Used in construction as crushed stone for road beds, landscaping, and as a raw material for glassmaking and silicon production. Smooth pebbles are popular in aquarium and decorative potting.
Geological facts
Quartzite is so tough that it often survives intense erosion that wears away surrounding softer rocks, often forming prominent ridges and hills. It is often harder than the steel blade of a knife.
Field identification & locations
Identify in the field by its sugary texture on fresh breaks and its inability to be scratched by steel. It is commonly found in riverbeds and mountainous regions where sedimentary beds have been folded and heated.
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