metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color typically ranging from white to gray, pink, or greenish due to impurities, vitreous to greasy luster, non-foliated crystal structure, lacks distinct cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color typically ranging from white to gray, pink, or greenish due to impurities, vitreous to greasy luster, non-foliated crystal structure, lacks distinct cleavage, specific gravity around 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. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used widely in construction as crushed stone for roadbeds, railway ballast, dimension stone, roofing granules, and in manufacturing silica brick and ferrosilicon.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often stand out as high ridges or peaks.
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, quartzite fractures across the quartz grains rather than around them.
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