sedimentary

Rounded brown river pebble

Indeterminate lithic fragment; likely weathered sandstone, mudstone, or fine-grained volcanic rock

AI-generated identification · may be incorrect

Hardness approximately 4–7 Mohs depending on composition; dull earthy luster, gray-brown color, fine-grained texture, and no visible cleavage or crystals. Its smooth, subtriangular shape indicates natural abrasion and transport.

Identified September 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as a consolidated sedimentary or fine-grained igneous rock, then rounded by water or glacial abrasion; its geological age cannot be determined from the image. Commonly derived from river gravel, beaches, or glacial deposits.

Uses & applications

Typically a decorative or curiosity pebble with negligible industrial value; similar material may be used as aggregate, landscaping stone, or polished stone.

Geological facts

The specimen’s exact identity cannot be confirmed visually because its grain size and internal structure are not exposed. A streak, hardness test, magnified examination, and fresh break would help distinguish sandstone, mudstone, and volcanic rock.

Field identification & locations

Look for bedding or sand grains for sandstone, a very smooth earthy fracture for mudstone, or tiny interlocking crystals and darker density for volcanic rock; common worldwide in stream and shoreline gravels.