metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or brown with vitreous luster; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or brown with vitreous luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, white, or brown with vitreous luster; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure, typically in orogenic belts. This specimen shows river-worn tumbling.
Uses & applications
Used widely in construction as crushed stone for road ballast, as a decorative building stone, and historically for stone tools due to its hardness and durability.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges and hilltops. It is one of the hardest common rocks found on the Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture that resembles sandpaper but feels smooth to the touch when polished or weathered.
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