metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Fracture: Conchoidal or irregular.
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Fracture: Conchoidal or irregular.
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events.
Uses & applications
Used extensively in road construction (aggregate), as a decorative stone in architecture, and as an industrial source of silica.
Geological facts
Quartzite is so hard and durable that it often forms the resistant caps of mountain ridges. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify by its extreme hardness and tendency to break through quartz grains rather than around them. Found globally in ancient tectonic regions like the Appalachians or the Alps.
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