fossil

Fossil crinoid columnal in limestone

Crinoidea indet.; calcitic ossicle (CaCO₃)

AI-generated identification · may be incorrect

Hardness about 3 (calcite), usually gray to tan, vitreous to dull luster, with visible layered/segmented structure and possible central canal. The specimen appears partly mineralized and enclosed in weathered carbonate matrix.

Identified August 27, 2026More fossil →

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Physical properties

Formation & geological history

Crinoid stem fragments accumulated in shallow Paleozoic seas and were buried and replaced or cemented by calcite, commonly during the Mississippian (~359–323 million years ago). Central Indiana near 39.4°N, 86.5°W is regionally plausible for Mississippian limestone fossils.

Uses & applications

Primarily a teaching, collecting, and decorative specimen; fossiliferous limestone may be used as aggregate or building stone, but this small piece has little industrial value.

Geological facts

Crinoid stems are made of many disk-like ossicles; weathered sections often show circular rings or a star-shaped lumen. Indiana is famous for abundant Mississippian crinoidal limestones.

Field identification & locations

Look for repeated coin-like segments, radial symmetry, and calcite reaction to dilute hydrochloric acid. A definitive identification would benefit from a close view of the specimen’s ends and any exposed cross-section; it could alternatively be a heavily weathered carbonate fragment.