metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or orange due to iron oxide impurities. It has a vitreous to greasy luster and a non-foliated, granular crystalline structure with conchoidal fracture and a specific gravity of around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or orange due to iron oxide impurities. It has a vitreous to greasy luster and a non-foliated, granular crystalline structure with conchoidal fracture and a specific gravity of around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperatures and pressures during regional metamorphism. Geological age varies widely depending on the formation region, ranging from Precambrian to Cenozoic eras.
Uses & applications
Used widely in construction as crushed stone for road bases, railway ballast, dimension stone, roofing granules, and in the manufacturing of refractory bricks and ferrosilicon.
Geological facts
Unlike sandstone, quartzite breaks across the quartz grains rather than around them, making it extremely durable and resistant to weathering and chemical attack.
Field identification & locations
Can be identified in the field by its inability to be scratched by a steel knife, lack of effervescence with acid, and the fused quartz grains visible on broken surfaces. Found worldwide in mountain-building belts.
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