metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors typically range from white to gray, pink, or reddish due to iron impurities. Luster is vitreous to greasy on fractured surfaces. Non-foliated massive crystal structure with interlocking quartz grains.
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Physical properties
Hardness of 7 on the Mohs scale, colors typically range from white to gray, pink, or reddish due to iron impurities. Luster is vitreous to greasy on fractured surfaces. Non-foliated massive crystal structure with interlocking quartz grains.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under intense heat and tectonic pressure, commonly in mountain-building events.
Uses & applications
Used in construction, road aggregate, manufacturing of silica bricks, railroad ballast, and occasionally as an ornamental stone or decorative gravel.
Geological facts
Unlike sandstone which breaks around sand grains, quartzite breaks straight through the quartz grains because the quartz cement binds them so tightly together.
Field identification & locations
Can be identified by its inability to be scratched by steel (hardness > 6.5) and its lack of effervescence with acid. Found worldwide in ancient mountain belts.
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