metamorphic
River Rock (Quartzite/Chert)
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: dull to waxy, Crystal structure: microcrystalline, Cleavage: none, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: dull to waxy, Crystal structure: microcrystalline, Cleavage: none, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of sandstone under high heat and pressure, often reshaped and smoothed over thousands of years by river transport and hydraulic action.
Uses & applications
Commonly used in landscaping, as a construction aggregate, and occasionally in decorative stone flooring or polished for hobbyist collections.
Geological facts
Quartzite is one of the most durable rocks on Earth's surface. This specific specimen shows signs of mechanical weathering and 'chatter marks' from hitting other rocks in a stream.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sandpaper-like texture inside broken surfaces. It is ubiquitous in riverbeds and glacial till throughout North America.
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