sedimentary

Rounded limestone or dolostone pebble

Calcite-rich limestone (CaCO₃), possibly dolostone (CaMg(CO₃)₂)

AI-generated identification · may be incorrect

Tan-gray, dull to earthy luster, fine-grained and water-worn; hardness about 3 for limestone or 3.5–4 for dolostone, with no visible cleavage or crystals. Likely reacts with dilute hydrochloric acid if calcitic, though weathering may mute the reaction.

Identified August 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud, shell debris, or altered limestone, then rounded by stream, beach, or glacial transport. The original sediment may range from Paleozoic to Cenozoic age; the pebble’s transport age is much younger.

Uses & applications

Common limestone is used for cement, aggregate, lime, and construction stone; individual pebbles have minimal commercial value but may be used in landscaping or collections.

Geological facts

Dark patches may be iron/manganese staining, organic material, or included fossil fragments. Its smooth shape indicates prolonged abrasion in moving water or surf.

Field identification & locations

Test an inconspicuous spot with vinegar or dilute acid: vigorous fizz supports calcitic limestone. A steel nail usually scratches it; dolostone fizzes weakly unless powdered. Common worldwide in carbonate terrains and riverbeds.