sedimentary

River Pebble (Quartzite/Siltstone)

Clastic Sedimentary Rock / Quartzite

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs); Color: Tan, beige, or brownish-grey; Luster: Dull to earthy; Texture: Fine-grained and water-worn; Structure: Rounded clast with no visible cleavage.

Hardness: 6-7 (Mohs)
Color: Tan, beige, or brownish-grey
Luster: Dull to earthy

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs); Color: Tan, beige, or brownish-grey; Luster: Dull to earthy; Texture: Fine-grained and water-worn; Structure: Rounded clast with no visible cleavage.

Formation & geological history

Formed from the lithification of silt or sand-sized grains, later rounded by mechanical weathering in a high-energy aquatic environment such as a riverbed or shoreline. These rocks can date back to any geological era from the Paleozoic to the Cenozoic.

Uses & applications

Common pebbles are used as aquarium gravel, in landscaping, as decorative mulch, in construction aggregate, and occasionally for rock tumbling by hobbyists.

Geological facts

The rounding of the stone is a result of a process called 'abrasion' or 'attrition,' where rocks collide with each other in moving water, wearing down sharp edges over hundreds or thousands of years.

Field identification & locations

Identify by its smooth, rounded exterior and fine-grained texture. It will not scratch easily with a steel knife if it is quartz-rich. Found globally in stream beds, beaches, and glacial deposits.