sedimentary

Rounded quartz-rich river pebble

Likely quartzite or quartz-rich sandstone; exact identification requires a fresh surface and tests

AI-generated identification · may be incorrect

Gray-brown, fine-grained, and strongly water-rounded with a dull to subtly granular luster; likely dominated by quartz (Mohs hardness 7), with possible feldspar, iron oxides, and minor cement. No obvious cleavage; density is typically about 2.6–2.7 g/cm³.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely weathered from a quartz-rich bedrock source and transported in a stream or glacial sediment; its precise geological age cannot be determined visually. The red spot probably represents iron-oxide staining or a minor altered mineral inclusion.

Uses & applications

Common pebbles have little commercial value, though attractive quartzite can be used as landscaping stone, aggregate, or decorative material; this specimen is not gem quality.

Geological facts

Its smooth shape records prolonged abrasion during transport. Quartz-rich rocks resist weathering, allowing them to survive as durable rounded cobbles.

Field identification & locations

Common in river gravels, beaches, and glacial deposits worldwide. A steel nail should not scratch it if quartzite; dilute hydrochloric acid should produce no reaction, helping distinguish it from carbonate rock. A fresh broken surface would improve identification.