metamorphic
Quartzite
Metamorphic Quartz Sandstone
Hardness of 7 on the Mohs scale, colors typically white to gray but can include pink, red, or green due to impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors typically white to gray but can include pink, red, or green due to impurities. Vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity around 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts, transforming the porous sandstone into a dense, interlocking rock.
Uses & applications
Used in construction as crushed stone for road bases, railway ballast, building facades, decorative landscaping, and occasionally as dimension stone or in manufacturing refractory bricks.
Geological facts
Quartzite is extremely resistant to weathering and erosion, which is why mountain ridges capped with quartzite often form prominent resistant peaks and crests.
Field identification & locations
Identified by its inability to be scratched by steel, lack of effervescence with acid, and the characteristic fractured surface that breaks through the quartz grains rather than around them. Found globally in mountainous regions and ancient cratons.
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