metamorphic
Quartzite
Quartzite (SiO2 silicon dioxide)
Mohs hardness of 7, high durability, vitreous to waxy luster, grainy or sugary texture, colors range from white to gray and reddish-brown, no cleavage (conchoidal fracture).
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Physical properties
Mohs hardness of 7, high durability, vitreous to waxy luster, grainy or sugary texture, colors range from white to gray and reddish-brown, no cleavage (conchoidal fracture).
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism), causing quartz grains to recrystallize and fuse together. Found in mountain ranges globally.
Uses & applications
Used in construction as road ballast, roofing granules, flooring, and wall cladding. Quality specimens are used in glass manufacturing and as sandpaper abrasives.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is often more resistant to weathering than the surrounding rock, often forming the crests of ridges and mountains.
Field identification & locations
Identify by its hardness (scratches glass) and sugary texture. Unlike sandstone, when broken, quartzite breaks through the quartz grains rather than around them.
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