sedimentary
Rounded quartz-rich pebble
Likely quartzite or quartz-rich sandstone; predominantly SiO₂
AI-generated identification · may be incorrectHardness about 6.5–7 if quartzite, or 5–7 if sandstone; tan-brown, granular, and dull to slightly vitreous. The rounded shape suggests water abrasion; individual grains and cleavage are not clearly visible.
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Physical properties
Hardness about 6.5–7 if quartzite, or 5–7 if sandstone; tan-brown, granular, and dull to slightly vitreous. The rounded shape suggests water abrasion; individual grains and cleavage are not clearly visible.
Formation & geological history
Likely formed from quartz sand lithified into sandstone, possibly recrystallized into quartzite, then weathered and rounded in a stream or beach environment. Its precise geological age cannot be determined from the photograph.
Uses & applications
Common specimens have little commercial value; quartzite is used as aggregate, roadstone, building stone, and occasionally decorative material.
Geological facts
Quartz-rich rocks commonly resist weathering, leaving rounded, durable pebbles. A scratch test with a steel knife and inspection for visible sand grains can help distinguish quartzite from sandstone.
Field identification & locations
Common in river gravels, beaches, glacial deposits, and weathered bedrock worldwide. It should scratch ordinary glass if quartz-rich; dilute acid should produce no reaction unless carbonate cement is present.
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