metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: White to grayish-white, Luster: Vitreous to dull, Crystal Structure: Trigonal (as quartz grains), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.6-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White to grayish-white, Luster: Vitreous to dull, Crystal Structure: Trigonal (as quartz grains), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing recrystallization of sand grains. Found in ancient metamorphic belts globally.
Uses & applications
Used in construction as crushed stone, road ballast, dimensional stone for countertops/flooring, and as a source of silica for glass manufacturing.
Geological facts
Quartzite is so durable that it often forms the resistant peaks of many mountain ranges. It is harder than steel and can scratch glass easily.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness (cannot be scratched by a knife). Commonly found in areas with tectonic fold belts such as the Appalachians or Alps.
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