metamorphic
Quartzite
Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color typically ranges from white to gray, pink, or green, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color typically ranges from white to gray, pink, or green, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity of 2.65.
Formation & geological history
Formed through the metamorphism of quartz sandstone or chert under high temperatures and tectonic pressures, recrystallizing the quartz grains into an intergrown mosaic.
Uses & applications
Used widely in construction, railroad ballast, decorative aggregates, walling stones, and manufacturing silica brick.
Geological facts
Unlike sandstone, quartzite will fracture across the quartz grains rather than around them when broken. It is extremely resistant to weathering and erosion, often forming prominent mountain ridges.
Field identification & locations
Can be identified in the field by its hard, crystalline texture, scratchability on glass, and lack of effervescence with hydrochloric acid. Commonly found in mountain belts worldwide.
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