metamorphic
Quartz-rich pebble, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂)
AI-generated identification · may be incorrectPale gray, massive, fine-grained, and dull to slightly glassy; quartz hardness is Mohs 7, with no cleavage and conchoidal to irregular fracture. The rounded shape and surface wear indicate a stream or glacial pebble.
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Physical properties
Pale gray, massive, fine-grained, and dull to slightly glassy; quartz hardness is Mohs 7, with no cleavage and conchoidal to irregular fracture. The rounded shape and surface wear indicate a stream or glacial pebble.
Formation & geological history
Quartzite forms when quartz-rich sandstone recrystallizes under heat and pressure during metamorphism; its exact geological age cannot be determined from the image. It commonly occurs in metamorphic mountain belts and as durable sediment in rivers and glacial deposits.
Uses & applications
Used as crushed stone, aggregate, road material, building stone, and occasionally decorative landscaping rock; attractive pieces may be collected but are rarely used as gemstones.
Geological facts
Quartzite is typically harder and more resistant to weathering than its parent sandstone. A scratch test against ordinary steel or glass can help distinguish it from softer gray rocks, though testing may damage the specimen.
Field identification & locations
Common in regions with exposed metamorphic terrain, including the Appalachians, Rocky Mountains, Scandinavia, and parts of Australia. A white streak, granular quartz texture, and lack of obvious layering support quartzite identification.
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