metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, or purple depending on impurities, vitreous to greasy luster, non-foliated 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, colors range from white and gray to pink, red, or purple depending on impurities, vitreous to greasy luster, non-foliated crystal structure, conchoidal fracture with no true cleavage, specific gravity around 2.65.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high temperatures and pressures usually associated with tectonic compression in orogenic belts. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, dimension stone, manufacturing silica brick, and occasionally as a decorative stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form prominent ridges and peaks.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily), the sugary texture on freshly broken surfaces, and the fact that individual quartz grains fuse across grain boundaries rather than fracturing around them like sandstone.
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