metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, purple, and reddish hues due to iron oxide impurities. Vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, purple, and reddish hues due to iron oxide impurities. Vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to intense heat and pressure, typically through regional metamorphism during tectonic mountain-building events.
Uses & applications
Used extensively in construction as crushed stone for roadbeds, railway ballast, building facades, and dimension stone, as well as in the manufacturing of refractory bricks and silica for metallurgical uses.
Geological facts
Unlike sandstone, which breaks around the grains, quartzite fractures straight through the quartz grains because the original quartz cement and grains recrystallized together into an interlocking mosaic, making it exceptionally durable and resistant to weathering.
Field identification & locations
Can be identified in the field by its inability to be scratched by steel, lack of reaction to hydrochloric acid, and the way fractured surfaces break directly across quartz grains rather than around them. Found globally in mountainous regions and ancient cratons.
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