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. Massive to granular crystal structure with no good cleavage, fracturing conchoidally.
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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. Massive to granular crystal structure with no good cleavage, fracturing conchoidally.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in mountain-building or tectonic compression zones over hundreds of millions of years.
Uses & applications
Used in construction, as crushed stone for road bases, in the manufacturing of refractory bricks, and occasionally as decorative stone or in countertops.
Geological facts
Because quartz is extremely durable and resistant to weathering, quartzite ridges often form prominent mountain crests and resistant landforms.
Field identification & locations
Can be identified in the field by its sugary texture, extreme hardness (it will easily scratch glass and cannot be scratched by a steel knife), and the fact that it breaks across the quartz grains rather than around them like sandstone.
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