fossil

Crinoid Fossil in Limestone

Crinoidea (Phylum Echinodermata) in Calcite Matrix (CaCO3)

Hardness: 3 on Mohs scale (matrix); Color: Tan, beige, or grey; Luster: Dull to earthy; Crystal structure: Hexagonal/rhombohedral (calcite); Cleavage: Perfect rhombohedral in fossils.

Hardness: 3 on Mohs scale (matrix)
Color: Tan, beige, or grey
Luster: Dull to earthy

Identified July 11, 2026More fossil →

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Physical properties

Hardness: 3 on Mohs scale (matrix); Color: Tan, beige, or grey; Luster: Dull to earthy; Crystal structure: Hexagonal/rhombohedral (calcite); Cleavage: Perfect rhombohedral in fossils.

Formation & geological history

Formed in marine environments during the Paleozoic Era (approx. 250-500 million years ago) when skeletal remains of sea lilies settled on the ocean floor and were lithified into limestone.

Uses & applications

Used primarily for educational purposes, paleontological study, and collector specimens. Massive deposits are used in the lime and construction industries.

Geological facts

Commonly known as 'sea lilies,' crinoids are not plants but animals related to starfish. The circular indentation seen here is the cross-section of a fossilized stem segment (columnal).

Field identification & locations

Look for circular or 'Cheerio' shaped impressions in sedimentary rocks, especially near old riverbeds or limestone quarries. They are ubiquitous in the Midwestern United States.

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Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

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Fossiliferous Limestone

Fossiliferous Calcilutite / Biomicrite

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Fossiliferous Limestone

Biogenic Limestone with Brachiopod/Crinoid fragments

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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