metamorphic
Quartzite
Metamorphic Quartz Rock (SiO2)
Hardness of 7 on the Mohs scale, color typically white to gray but can feature pink or reddish hues due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure, lacks prominent cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color typically white to gray but can feature pink or reddish hues due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure, lacks prominent cleavage, specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure, typically during mountain-building events over millions of years.
Uses & applications
Used widely in construction as crushed stone for road bases, railroad ballast, dimension stone, roofing granules, and in the manufacturing of refractory bricks and silica.
Geological facts
Because quartz is extremely resistant to weathering, quartzite mountains and ridges often stand out prominently in the landscape as resistant ridges.
Field identification & locations
Can be identified in the field by its sugary texture, inability to be scratched by a steel knife (hardness > 5.5), and the way it breaks across the quartz grains rather than around them like sandstone.
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