metamorphic
Rounded quartz-rich pebble, likely quartzite
Quartzite (mostly microcrystalline SiO₂), possibly a weathered quartz-rich sandstone or vein quartz
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray-white, dull to weakly vitreous luster, dense and fine-grained with faint mottling. No obvious cleavage; irregular fracture and a water-worn rounded shape are visible.
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Physical properties
Hardness about 7 Mohs; pale gray-white, dull to weakly vitreous luster, dense and fine-grained with faint mottling. No obvious cleavage; irregular fracture and a water-worn rounded shape are visible.
Formation & geological history
Likely formed when quartz sandstone recrystallized under heat and pressure during regional metamorphism, then eroded and rounded by transport in a river or beach. Its precise age and source cannot be determined from the photograph.
Uses & applications
Common quartzite is used as aggregate, landscaping stone, road material, and dimension stone; attractive pieces may be tumbled or collected. This specimen appears ordinary and is unlikely to be suitable for jewelry.
Geological facts
Quartzite commonly resists weathering better than surrounding rocks, producing durable pebbles and ridges. A glass-scratch test can support identification, though it may mark the specimen.
Field identification & locations
Common worldwide, especially in river gravels and near metamorphic mountain belts; notable sources include the Appalachians, Rocky Mountains, India, Brazil, and Scandinavia. Confirm with a hardness test, close inspection for interlocking quartz grains, and ideally acid and thin-section testing.
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