sedimentary

Polished fossiliferous limestone pebble

Fossiliferous micritic limestone, chiefly calcite (CaCO₃)

AI-generated identification · may be incorrect

Dark gray, fine-grained, rounded and water-worn, with pale branching or shell-like fossil markings; dull to slightly waxy luster. Calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.7; it should fizz with dilute hydrochloric acid or strong vinegar if exposed.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Marine carbonate mud accumulated on an ancient seafloor and lithified, preserving shells, corals, or burrows; its exact geological age cannot be determined from the photograph. Later erosion rounded it into a pebble, likely in a river, beach, or gravel deposit.

Uses & applications

Used mainly as a teaching, lapidary, or ornamental specimen; limestone is also important for cement, lime, aggregate, and building stone. This small piece has modest collector value.

Geological facts

The white patterns may be fossil fragments, veins, or weathered calcite-filled fractures; close inspection or acid testing is needed to distinguish them. Fossiliferous limestone commonly records shallow, warm marine environments.

Field identification & locations

Common in sedimentary basins, limestone quarries, beaches, and stream gravels worldwide; examine broken surfaces with a hand lens and test hardness against a steel knife. Estimated value: $1–$10, or roughly $10–$30 if fossil details are unusually clear and attractively polished.