Rock Identifier
Fossiliferous Limestone (Crinoid stem fossils) (Sedimentary Limestone with Crinoidea ossicles) — fossil
fossil

Fossiliferous Limestone (Crinoid stem fossils)

Sedimentary Limestone with Crinoidea ossicles

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale), Color: Dark grey to charcoal, Luster: Dull/Earthy, Crystal Structure: Microcrystalline matrix with calcitic fossil inclusions, Cleavage: None (conchoidal to irregular fracture)

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Physical properties

Hardness: 3-4 (Mohs scale), Color: Dark grey to charcoal, Luster: Dull/Earthy, Crystal Structure: Microcrystalline matrix with calcitic fossil inclusions, Cleavage: None (conchoidal to irregular fracture)

Formation & geological history

Formed in shallow marine environments during the Paleozoic era (approx. 250-500 million years ago) from the accumulation of calcium carbonate and skeletal remains of marine organisms.

Uses & applications

Primarily used as decorative stones, educational specimens for paleontology, and in aggregate for construction or lime production.

Geological facts

Crinoids are also known as 'sea lilies'. The circular and C-shaped patterns on the surface are cross-sections of the animal's segmented stem made of stacked discs called columnals.

Field identification & locations

Identify by its reaction to cold dilute hydrochloric acid (bubbles) and the presence of distinct circular or wheel-like patterns. Common in Great Lakes regions and areas with ancient seabed deposits.

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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

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