metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: White, gray, yellowish-brown to reddish due to iron oxide staining. Luster: Vitreous to dull. Fracture: Conchoidal to uneven. Texture: Granoblastic, highly interlocking quartz grains.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: White, gray, yellowish-brown to reddish due to iron oxide staining. Luster: Vitreous to dull. Fracture: Conchoidal to uneven. Texture: Granoblastic, highly interlocking quartz grains.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under intense heat and high pressure. The original quartz grains recrystallize and fuse together tightly.
Uses & applications
Widely used as decorative landscape boulders, dimension stone in architecture, railway ballast, aggregate in construction, and crushed stone for silica glass production.
Geological facts
Quartzite is so hard and tough that when it breaks, it fractures right through the quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Look for a sugary, crystalline appearance on fresh surfaces, extreme hardness (scratches glass easily), and iron staining on weathered surfaces. Very common in mountainous metamorphic terrains worldwide.
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