metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: Grayish-brown with tan banding in this specimen. Luster: Vitreous to waxy. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-brown with tan banding in this specimen
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale. Color: Grayish-brown with tan banding in this specimen. Luster: Vitreous to waxy. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. It can be found in mountain belts and shield areas dating from the Proterozoic to more recent eras.
Uses & applications
Used as crushed stone for road construction, railroad ballast, and as a decorative stone in landscaping. High-quality slabs are used for countertops and flooring.
Geological facts
Quartzite is so tough that it often survives intense weathering better than the surrounding rocks, frequently forming the summits of ridges and mountains. It is harder than a steel knife and will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and smooth, water-worn texture in river deposits. Look for a sugary appearance on fresh breaks. It is commonly found in glacial till or riverbeds in regions with metamorphic bedrock.
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