metamorphic
Quartzite
Quartzite (Metamorphic Rock)
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, green, yellow, or blue, vitreous to greasy luster, massive to granular crystal structure, conchoidal fracture with indistinct cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, green, yellow, or blue, vitreous to greasy luster, massive to granular crystal structure, conchoidal fracture with indistinct cleavage, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional or contact metamorphism. Geological age spans from Precambrian to Cenozoic.
Uses & applications
Used in construction, as road aggregate, railroad ballast, dimension stone, manufacture of silica brick, and sometimes as a decorative stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. Mountain ranges like the Appalachian peaks often feature prominent quartzite ridges because it resists erosion much better than surrounding rocks.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces, high hardness (scratches glass easily), and the fact that it breaks through the quartz grains rather than around them, unlike sandstone.
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