sedimentary

Crinoid Fossil in Limestone

Crinoid (Class Crinoidea) in Fossiliferous Limestone (CaCO3)

Hardness: 3 (calcite matrix); Color: Grey, tan, or white; Luster: Dull to earthy; Structure: Cylindrical segmented columnals often resembling a screw or stack of coins; Cleavage: Perfect rhombohedral in individual calcite crystals.

Hardness: 3 (calcite matrix)
Color: Grey, tan, or white
Luster: Dull to earthy

Identified March 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of organic debris on the seafloor during the Paleozoic era (approx. 250-500 million years ago). The specimen represents the calcified stem of a 'sea lily' marine animal preserved in calcium carbonate mud.

Uses & applications

Used primarily for educational purposes, scientific study (paleontology), and by amateur rock/fossil collectors. The limestone matrix may be used in construction or cement production if found in large deposits.

Geological facts

Crinoids are actually animals related to starfish and sea urchins, not plants. They were so abundant in the Mississippian subperiod that it is often called the 'Age of Crinoids.'

Field identification & locations

Identify in the field by looking for the distinct 'zipper-like' or 'cogwheel' patterns in sedimentary rock layers. Common in limestone outcrops, riverbeds, and quarries across the Midwest USA and UK.

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