fossil

Crinoid fossil in limestone

Crinoidea fossil, commonly preserved in bioclastic calcitic limestone (CaCO₃)

AI-generated identification · may be incorrect

Gray-beige, granular limestone containing abundant circular crinoid columnals and a prominent stem segment; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7.

Identified August 29, 2026More fossil →

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Physical properties

Formation & geological history

Marine crinoids lived on Paleozoic seafloors, especially during the Mississippian and Ordovician periods (roughly 485–323 million years ago). Their disarticulated calcite skeletons accumulated, were compacted, and cemented into fossiliferous limestone.

Uses & applications

Used primarily for education, paleontology, and collecting; occasionally cut and polished as decorative stone or jewelry. It has little industrial value as an individual specimen.

Geological facts

The round discs are stem columnals, often called “stone lilies”; the larger segmented structure may be part of a crinoid stem or arm. Crinoid-rich limestones are commonly called crinoidal limestone.

Field identification & locations

Identify by repeated circular discs with central holes, star-like symmetry, and fossil fragments embedded in carbonate rock; dilute hydrochloric acid will fizz on fresh surfaces. Common in Paleozoic marine limestones worldwide, especially the Midwest United States and England.