sedimentary

Crinoid Fossil in Limestone

Class Crinoidea in Carbonate Matrix (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (matrix), color: grey and tan/yellowish iron staining, luster: dull/earthy, structure: cylindrical disk-stacking (columnals) with pentagonal or circular symmetry, cleavage: rhombohedral in calcite crystals.

Identified March 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed during the Paleozoic era (approx. 300-500 million years ago) in shallow marine environments. The skeleton of the sea lily settled in lime mud, which lithified into limestone over millions of years.

Uses & applications

Educational specimens, museum displays, landscaping, and paleontology research. Crinoidal limestone is sometimes used as decorative 'fossil marble' in architecture.

Geological facts

Crinoids are known as 'sea lilies' but are actually animals related to starfish and sea urchins. Their stems are often found fragmented into small 'cheerio' shaped pieces called columnals, which were once used as prayer beads (St. Cuthbert's beads).

Field identification & locations

Identify by the characteristic 'screw-like' or stacked-disk impression in fine-grained sedimentary rock. Found globally in limestone outcrops, particularly in the Midwest US, UK, and Morocco. Look for segments with a central hole.