sedimentary

Tumbled fossiliferous limestone

Fossiliferous micritic limestone, mainly calcite (CaCO₃)

AI-generated identification · may be incorrect

Brown, smoothly water-worn specimen with pale fossil or shell fragments and darker inclusions; calcite has Mohs hardness 3, vitreous-to-dull luster, rhombohedral cleavage, and specific gravity about 2.7. Effervesces with dilute hydrochloric acid, though a polished surface may react weakly.

Identified September 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from accumulated marine skeletal debris and carbonate mud later compacted and lithified; its age cannot be determined reliably from the photograph, but such limestone commonly ranges from Paleozoic to Cenozoic. The rounded shape indicates beach, river, or intentional tumbling and polishing.

Uses & applications

Used as a decorative and educational specimen, aggregate, building stone, and cement feedstock; attractive pieces may be used in lapidary collections or cabochons.

Geological facts

Visible circular and irregular markings may be fossil fragments, shell sections, or weathered mineral-filled cavities rather than true crystals.

Field identification & locations

Common in carbonate terrains and coastal gravels worldwide; inspect for identifiable shell, coral, or crinoid structures and test an inconspicuous area with acid. Approximate value: $2–$15 as a small common specimen, or $15–$40 if fossils are especially clear.