Rock Identifier
Crinoid Fossil in Limestone (Crinoid columnal (Class Crinoidea) in biomicrite) — fossil
fossil

Crinoid Fossil in Limestone

Crinoid columnal (Class Crinoidea) in biomicrite

Hardness: 3 (calcite matrix); Color: Off-white, tan, and grey; Luster: Dull/earthy matrix with slightly vitreous fossil; Structure: Distinctive segmented cylindrical stem fragments; Cleavage: perfect rhombohedral in calcite crystals.

Hardness
3 (calcite matrix)
Color
Off-white, tan, and grey
Luster
Dull/earthy matrix with slightly vitreous fossil
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Physical properties

Hardness: 3 (calcite matrix); Color: Off-white, tan, and grey; Luster: Dull/earthy matrix with slightly vitreous fossil; Structure: Distinctive segmented cylindrical stem fragments; Cleavage: perfect rhombohedral in calcite crystals.

Formation & geological history

Formed in shallow marine environments during the Paleozoic era (approx. 250-500 million years ago). Crinoids, also known as sea lilies, are echinoderms whose skeletons are made of calcite discs that stack to form stems.

Uses & applications

Educational specimens, museum exhibits, decorative stone, and of high interest to amateur fossil collectors.

Geological facts

Crinoids are actually animals related to starfish and sea urchins, not plants. They were so numerous in the Mississippian Period that some limestone layers are composed almost entirely of their remains.

Field identification & locations

Identified by 'Cheerios-like' or gear-shaped impressions and cylindrical segments in sedimentary rock. Commonly found in road cuts and stream beds in the Midwest United States and UK.

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