metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, or yellow due to iron oxide impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, or yellow due to iron oxide impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity of 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under intense heat and tectonic pressure, typically in mountain-building events over millions of years.
Uses & applications
Used widely in construction, railway ballast, manufacturing of silica bricks, decorative building stone, and occasionally as a gemstone or countertop material.
Geological facts
Unlike sandstone, quartzite breaks across the quartz grains rather than around them, demonstrating its superior strength and complete recrystallization.
Field identification & locations
Can be identified in the field by its inability to be scratched by steel, lack of fizzing with acid, and a sugary, sparkling texture on broken surfaces. Found worldwide in ancient mountain belts.
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