metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or brown due to iron oxide impurities. Vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, no true cleavage, and a specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or brown due to iron oxide impurities. Vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, no true cleavage, and a specific gravity of 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and tectonic pressures, typically dating from various geological eras from the Precambrian onward.
Uses & applications
Used in construction, as crushed stone for road bases, in railroad ballast, for manufacturing silica brick, and occasionally as an ornamental stone or decorative aggregate.
Geological facts
Unlike sandstone, which breaks around the individual grains, quartzite fractures directly across the grains due to the intense pressure and heat fusing them tightly together.
Field identification & locations
Can be identified by its extreme hardness (will easily scratch glass and cannot be scratched by a knife) and its lack of effervescence with acid. Commonly found in mountainous regions and old orogenic belts worldwide.
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