sedimentary

Weathered limestone pebble

Microcrystalline calcite (CaCO₃), possibly fossiliferous limestone

AI-generated identification · may be incorrect

Typically Mohs hardness 3, light cream to tan, dull to faintly earthy luster, and fine-grained massive texture; calcite commonly reacts vigorously with dilute hydrochloric acid or vinegar. The rounded, irregular specimen appears weathered and may contain subtle fossil or sediment textures.

Identified September 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud or shell debris, commonly in shallow marine settings; its exact geological age cannot be determined from the photograph. Natural abrasion likely produced the smooth pebble shape.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, soil amendment, and decorative material; attractive fossiliferous pieces are collected but this specimen appears low-value.

Geological facts

Limestone is primarily calcite and can dissolve in weak acid, contributing to caves, karst landscapes, and sinkholes. A positive acid fizz helps distinguish it from many similarly colored silicate rocks.

Field identification & locations

Common in limestone regions, river gravels, beaches, and glacial deposits. Identify it by its pale color, relatively soft surface, lack of visible crystals, and acid reaction; avoid confusing it with weathered concrete.