metamorphic
Quartzite
Metamorphic Quartz Rock (SiO2)
Hardness of 7 on the Mohs scale, typically white, gray, or pinkish-gray in color, vitreous to greasy luster, massive to granular 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, typically white, gray, or pinkish-gray in color, vitreous to greasy luster, massive to granular crystal structure, conchoidal fracture with no true cleavage, specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and pressures, typically in tectonic mountain-building zones over millions of years.
Uses & applications
Used in construction, road aggregate, railroad ballast, manufacturing of silica bricks, and occasionally as decorative stone or in lapidary arts.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ancient quartz sandstone ridges often survive as prominent ridges and mountains after surrounding softer rock erodes away.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), inability to be scratched by a knife, and the way it breaks across quartz grains rather than around them like sandstone. Found worldwide.
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