metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White, tan, or iron-stained orange/brown, Luster: Vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White, tan, or iron-stained orange/brown, Luster: Vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to extreme heat and pressure, causing quartz grains to recrystallize and fuse into a dense rock.
Uses & applications
Used extensively in road construction, railway ballast, flooring, countertops, and high-purity varieties are used in glass-making.
Geological facts
Quartzite is one of the most durable and weather-resistant rocks on Earth. While it looks like marble, it is much harder and will not react to acid.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary texture. Common in ancient mountain ranges and riverbeds.
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