metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, brown, or green, vitreous to greasy luster, non-foliated crystal structure, conchoidal fracture, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, brown, or green, vitreous to greasy luster, non-foliated crystal structure, conchoidal fracture, specific gravity of 2.65.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high heat and pressure, typically through tectonic compression in orogenic belts.
Uses & applications
Used in construction, as crushed stone for road bases, in manufacturing railroad ballast, and occasionally as a decorative building stone or for countertops.
Geological facts
Because quartz is extremely durable and resistant to chemical weathering, quartzite ridgetops often form prominent resistant hills and mountains in folded mountain belts.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), inability to be scratched by a knife, and the way it breaks across quartz grains rather than around them like sandstone. Found worldwide.
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