metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs), Color: Light gray/white with greenish-blue tints, Luster: Vitreous to greasy, Structure: Granular or crystalline, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: Light gray/white with greenish-blue tints, Luster: Vitreous to greasy, Structure: Granular or crystalline, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse into a dense network.
Uses & applications
Used in construction as road ballast, roofing material, and flooring. Used as an abrasive and in the production of glass and ferrosilicon.
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rock, forming resistant ridges and hilltops in mountainous terrains. It will scratch steel and glass easily.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and its granular appearance which looks like sparkling grains of sugar. Commonly found in folded mountain ranges.
