metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color typically ranges from white to gray, pink, or yellowish due to iron oxide impurities. Luster is vitreous to greasy on fractured surfaces. Crystal structure is trigonal/microcrystalline. Conchoidal fracture, no distinct cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color typically ranges from white to gray, pink, or yellowish due to iron oxide impurities. Luster is vitreous to greasy on fractured surfaces. Crystal structure is trigonal/microcrystalline. Conchoidal fracture, no distinct cleavage, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional metamorphism. Geological age varies greatly, spanning from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, building facades, decorative landscaping, and occasionally as a dimension stone or countertop material.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form prominent ridges and peaks. It is hard enough to scratch glass.
Field identification & locations
Identified in the field by its extreme hardness (scratches steel and glass), lack of reaction to hydrochloric acid, and granular sugar-like texture on freshly broken surfaces. Found worldwide in ancient mountain belts.
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