metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; colors range from white and gray to pink, brown, or yellowish due to iron oxide impurities; vitreous to greasy luster; non-foliated crystal structure; lacks distinct cleavage; specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; colors range from white and gray to pink, brown, or yellowish due to iron oxide impurities; vitreous to greasy luster; non-foliated crystal structure; lacks distinct cleavage; specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and tectonic pressures, often dating back hundreds of millions of years.
Uses & applications
Used in construction, road aggregate, railway ballast, dimension stone, and occasionally for countertops and decorative landscaping.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often stand out as high ridges after surrounding softer rocks have eroded away.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily) and the way it breaks across quartz grains rather than around them, unlike sandstone.
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