metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness: 7 on the Mohs scale, Color: Brownish-grey with iron-oxide staining, Luster: Vitreous to greasy, Crystal structure: Trigonal (microcrystalline quartz grains), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: Brownish-grey with iron-oxide staining, Luster: Vitreous to greasy, Crystal structure: Trigonal (microcrystalline quartz grains), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to regional or contact metamorphism involving high heat and pressure, typically over hundreds of millions of years.
Uses & applications
Used in construction, railroad ballast, crushed stone for road aggregates, and decorative landscaping. Weathered pebbles are often collected as garden stones.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstone survives transport in rivers and oceans to become smooth pebbles.
Field identification & locations
Can be identified by its high hardness (scratches glass easily), lack of effervescence with acid, and sugary textured fractured surfaces. Commonly found in riverbeds, beaches, and glacial deposits worldwide.
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