metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, typically gray, brown, or white in color, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically gray, brown, or white in color, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone under intense heat and pressure deep within the Earth's crust, typically during mountain-building tectonic events (orogeny) over millions of years.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, manufacturing silica bricks, and occasionally as decorative stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often survive as prominent hills or mountain crests.
Field identification & locations
Can be identified in the field by its sugary texture, inability to be scratched by a steel knife, and the fact that it breaks across the quartz grains rather than around them.
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