fossil

Crinoid Stem Fossil (St John's Bead)

Crinoidea (Class)

Hardness: 3 (calcite composition). Color: Tan, brown, gray, to buff. Luster: Dull to earthy. Structure: Disc-shaped fossil columnal with a central hole (axial canal) and grooved/scalloped edges. Specific gravity: ~2.7.

Hardness: 3 (calcite composition)
Color: Tan, brown, gray, to buff
Luster: Dull to earthy

Identified July 26, 2026More fossil →

Explore Crinoid Stem Fossil (St John's Bead) in the encyclopedia →

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Physical properties

Formation & geological history

Formed from the calcite skeletal segments (columnals) of ancient marine animals called crinoids (sea lilies) that lived in shallow marine environments. Dates typically from the Ordovician to the Permian periods (approx. 500 to 250 million years ago).

Uses & applications

Used primarily for educational display, fossil collections, and historically as beads for jewelry and rosaries.

Geological facts

Also known historically as 'St. Cuthbert's beads' or 'star stones'. Although they resemble plants, crinoids were marine echinoderms related to modern starfish and sea urchins.

Field identification & locations

Identified by the circular or star-shaped cross-section with a central lumen and ribbed edges. Commonly found in limestone beds throughout the American Midwest, the UK, and ancient marine deposits worldwide.

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Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

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Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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Fossiliferous Limestone

Fossiliferous Calcilutite / Biomicrite

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