metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None/clastic fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None/clastic fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, where individual quartz grains recrystallize into a locked mosaic. Found in orogenic belts worldwide.
Uses & applications
Used extensively in construction as crushed stone or road ballast, as dimension stone for wall coverings and flooring, and occasionally as a source of silica in glass manufacturing.
Geological facts
Quartzite is so durable that it can survive the intense mechanical weathering of rivers and glacial movement, often appearing as rounded cobbles. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (scratches glass) and sand-like texture that does not rub off. Look for it in riverbeds or mountain ranges. High-purity white varieties are prized by collectors.
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