metamorphic
Quartzite
Quartzite (Metamorphosed Sandstone)
Hardness: 7 on the Mohs scale, Color: Typically tan, brown, white, or gray, Luster: Vitreous to greasy, Crystal structure: Interlocking quartz grains, Cleavage: None (fractures conchoidally), Specific gravity: 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: Typically tan, brown, white, or gray, Luster: Vitreous to greasy, Crystal structure: Interlocking quartz grains, Cleavage: None (fractures conchoidally), Specific gravity: 2.65
Formation & geological history
Formed under high heat and pressure from quartz-rich sandstone during regional or contact metamorphism, often ranging in age from Precambrian to Cenozoic depending on the specific geological formation.
Uses & applications
Used in construction, as railroad ballast, in decorative landscaping, for manufacturing silica brick and ferrosilicon, and occasionally as a decorative or countertop stone.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form the highest ridges and peaks in an area.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces, high hardness that scratches glass easily, and the fact that it does not fizz with hydrochloric acid.
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