metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, typically white, gray, or pinkish due to iron oxide impurities, vitreous to greasy luster, non-foliated dense crystal structure, conchoidal fracture with no true cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white, gray, or pinkish due to iron oxide impurities, vitreous to greasy luster, non-foliated dense crystal structure, conchoidal fracture with no true cleavage, specific gravity around 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression during mountain-building events (regional metamorphism). Geological age ranges from Precambrian to Cenozoic.
Uses & applications
Used in construction, road aggregate, railroad ballast, dimension stone, and manufactured countertops, as well as crushed stone for building foundations.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form the highest ridges and peaks in many mountain ranges.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), sugary texture on broken surfaces, and the fact that unlike sandstone, it breaks across the quartz grains rather than around them. Found globally worldwide.
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