metamorphic
Quartzite
Metamorphic Quartz Rock (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, brown, and yellowish due to iron oxide impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains. Conchoidal fracture and no true cleavage.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, brown, and yellowish due to iron oxide impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains. Conchoidal fracture and no true cleavage.
Formation & geological history
Formed from quartz-rich sandstone or chert under high heat and tectonic pressure during regional or contact metamorphism. The original sand grains recrystallize and weld together tightly.
Uses & applications
Used in construction, road aggregate, railway ballast, manufacturing of silica bricks, and occasionally as a decorative stone or countertop material.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich mountain ridges often stand out as high crests in many landscapes.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily), inability to be scratched by a knife, and the sugary texture of interlocking quartz crystals visible on broken surfaces. Found worldwide.
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