sedimentary

Rounded river pebble, likely altered limestone or sandstone

Probable micritic limestone (calcite-rich, CaCO₃) or fine-grained sandstone

AI-generated identification · may be incorrect

Pale gray-green, matte to weakly earthy luster, fine-grained and smoothly water-worn; apparent hardness about 3–6 Mohs depending on composition, with no visible crystals or cleavage. A limestone specimen should fizz with dilute hydrochloric acid or vinegar, whereas sandstone generally will not.

Identified August 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as sedimentary rock, then rounded by abrasion in a stream, beach, or gravel deposit; its precise geological age and formation setting cannot be determined from the image.

Uses & applications

Commonly collected as a pebble or used decoratively in landscaping and crafts; not suitable for gemstone jewelry and has little industrial value at this size.

Geological facts

The greenish tint may result from clay minerals, chlorite, or weathering rather than a distinct green mineral. Surface rounding indicates prolonged transport or wave action.

Field identification & locations

Look for acid reaction, gritty texture, visible sand grains, and a white powdery streak to distinguish limestone from sandstone; common worldwide in riverbeds and beaches.