metamorphic
Quartzite
Metamorphic Quartzite
Hardness of 7 on the Mohs scale; colors range from white and gray to pink, brown, or yellow due to iron oxide impurities; vitreous to greasy luster; non-foliated massive crystal structure with interlocking quartz grains.
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Physical properties
Hardness of 7 on the Mohs scale; colors range from white and gray to pink, brown, or yellow due to iron oxide impurities; vitreous to greasy luster; non-foliated massive crystal structure with interlocking quartz grains.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure, commonly dating from various geological eras.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, manufacturing of silica bricks, decorative landscaping, and occasionally as a dimension stone.
Geological facts
Unlike sandstone, which breaks around the sand grains, quartzite breaks straight through the quartz grains due to the strong interlocking silica cement formed under intense heat and pressure.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily), inability to be scratched by a steel knife, and lack of effervescence when tested with acid. Found worldwide in mountain belts and ancient cratons.
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