metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; white, yellowish, or reddish-brown color; vitreous to greasy luster; non-foliated, massive 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; white, yellowish, or reddish-brown color; vitreous to greasy luster; non-foliated, massive crystal structure; conchoidal fracture with no true cleavage; specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to high heat and pressure, typically through tectonic compression in orogenic belts, over millions of years.
Uses & applications
Used in construction, as crushed stone for roadbeds, in manufacturing railroad ballast, as dimension stone, and for refractory bricks.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstones turn into nearly indestructible ridges when metamorphosed.
Field identification & locations
Identified by its high hardness (scratches glass easily), lack of effervescence with acid, and the fused quartz grains that break across the grains rather than around them. Found globally worldwide in mountain belts.
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