Rock Identifier
Fossiliferous limestone, likely coral or shell-rich limestone (Biogenic calcite (CaCO₃), commonly limestone containing fossil coral or mollusks) — fossil
fossil

Fossiliferous limestone, likely coral or shell-rich limestone

Biogenic calcite (CaCO₃), commonly limestone containing fossil coral or mollusks

AI-generated identification · may be incorrect

Typically Mohs hardness 3, white to tan or gray, dull to earthy luster, and irregular granular texture; calcite may show rhombohedral cleavage. The visible porous cavity and rounded fossil textures suggest a biogenic limestone rather than a crystalline mineral.

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Physical properties

Typically Mohs hardness 3, white to tan or gray, dull to earthy luster, and irregular granular texture; calcite may show rhombohedral cleavage. The visible porous cavity and rounded fossil textures suggest a biogenic limestone rather than a crystalline mineral.

Formation & geological history

Formed from accumulated marine skeletal material that lithified into limestone, commonly during Paleozoic–Cenozoic shallow-marine deposition; the cavity may reflect dissolved fossils or weathering.

Uses & applications

Used as aggregate, cement and dimension stone when sound; attractive fossiliferous pieces are mainly collected or displayed rather than used in jewelry.

Geological facts

Calcite-rich limestone effervesces vigorously with dilute hydrochloric acid or household vinegar, though vinegar may react slowly. Coral fossils often preserve repeated corallite pores or honeycomb-like structures.

Field identification & locations

Common in former shallow seas worldwide, including Florida, the Caribbean, Mediterranean regions and many coastal sedimentary basins. Check for acid reaction, low hardness, and identifiable fossil patterns; avoid assuming every hole is a fossil cavity.

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Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

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Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

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Crinoid Stem Fossil in Matrix (Phylum Echinodermata, Class Crinoidea) — fossil

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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Fossiliferous limestone (likely a crinoidal or shell-fragment limestone) (Bioclastic limestone, composed chiefly of calcite (CaCO₃)) — sedimentary

Fossiliferous limestone (likely a crinoidal or shell-fragment limestone)

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

sedimentary
Porous limestone pebble (Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image) — sedimentary

Porous limestone pebble

Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image

sedimentary
Weathered fossil bone fragment (identification uncertain) (Fossilized bone; exact taxon and mineral composition cannot be determined from the image) — fossil

Weathered fossil bone fragment (identification uncertain)

Fossilized bone; exact taxon and mineral composition cannot be determined from the image

fossil