metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, green, or yellow due to impurities, vitreous to greasy luster, granular crystal structure, no good 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, or yellow due to impurities, vitreous to greasy luster, granular crystal structure, no good cleavage, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional metamorphism, often during mountain-building events over millions of years.
Uses & applications
Used in construction, as crushed stone for road bases, in manufacturing railroad ballast, in the production of silica brick, and occasionally as a decorative stone or in lapidary arts.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often persist as prominent hills or mountain crests.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces and the fact that it will scratch glass and cannot be scratched by a knife. Unlike sandstone, it breaks across quartz grains rather than around them.
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