sedimentary

Rounded quartz-rich river pebble

Likely quartzite or quartz-rich sandstone; predominantly SiO₂

AI-generated identification · may be incorrect

Hardness about 6.5–7, pale cream to tan, dull to subtly vitreous luster, massive granular texture, and no obvious cleavage. The rounded shape and surface wear indicate water transport; exact identification requires a hardness and acid test.

Identified September 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably a weathered and rounded fragment of quartzite or strongly cemented sandstone, formed from older silica-rich sediment and later lithified or metamorphosed. Its precise geological age and source cannot be determined from the photograph.

Uses & applications

Primarily a natural pebble or teaching/collecting specimen; quartzite is also used as aggregate, road stone, and dimension stone. This ordinary example has little commercial value.

Geological facts

Quartz-rich rocks commonly resist weathering, allowing them to persist as rounded stream cobbles. Brown patches likely reflect iron-oxide staining or weathered impurities.

Field identification & locations

Common in streambeds, gravel deposits, and glacial sediments. A steel nail should not scratch it, while quartz or glass should; dilute hydrochloric acid should produce no fizz, distinguishing it from limestone.