metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: White, gray, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal; Fracture: Granular or conchoidal; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal; Fracture: Granular or conchoidal; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This causes the quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used widely in construction as crushed stone for road ballast, floor tiles, wall coverings, and countertops. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so tough that it often survives the weathering process longer than surrounding rocks, frequently forming the peaks of ridges and mountains. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify in the field by its sugary, granular texture and extreme hardness (it cannot be scratched by a knife). It is found globally in mountainous regions where tectonic activity has occurrred.
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