sedimentary
Crinoid Fossil in Limestone
Class Crinoidea in Carbonate Matrix (CaCO3)
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.
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Physical properties
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.
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.
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