Rock Identifier
Polished fossiliferous limestone (Fossiliferous micrite/bioclastic limestone, likely crinoidal or shell-rich limestone) — fossil
fossil

Polished fossiliferous limestone

Fossiliferous micrite/bioclastic limestone, likely crinoidal or shell-rich limestone

AI-generated identification · may be incorrect

Dark gray to black, polished, fine-grained carbonate containing numerous circular fossil cross-sections; calcite composition, Mohs hardness 3, dull to glossy polish, and typically massive structure with no cleavage visible. It may fizz weakly with dilute hydrochloric acid.

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Physical properties

Dark gray to black, polished, fine-grained carbonate containing numerous circular fossil cross-sections; calcite composition, Mohs hardness 3, dull to glossy polish, and typically massive structure with no cleavage visible. It may fizz weakly with dilute hydrochloric acid.

Formation & geological history

Formed when marine skeletal debris accumulated, compacted, and cemented as limestone, commonly during the Paleozoic or Mesozoic eras. The circular patterns are likely fossil fragments such as crinoid stems, shells, or coral.

Uses & applications

Used as a decorative polished stone, cabochon, paperweight, or educational fossil specimen; not generally used structurally in this small polished form.

Geological facts

The repeated ring-like features preserve marine organisms in cross-section and are characteristic of fossiliferous carbonate rocks. Exact fossil identification requires magnification and locality information.

Field identification & locations

Look for visible fossil outlines, carbonate softness, and acid effervescence; common sources include fossil-bearing limestones in the United States, United Kingdom, Europe, and North Africa. Avoid prolonged acid testing because it damages the polish.

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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)

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Porous limestone pebble

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

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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

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