fossil

Crinoid Columnal Fossil in Chert

Crinoidea stemming section in Microcrystalline Quartz (SiO2)

Hardness: 7 (Mohs scale), Color: Rusty brown to tan due to iron staining, Luster: Waxy to dull, Structure: Circular/donut-shaped central cavity (lumen) within a silicified matrix.

Identified July 4, 2026More fossil →

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Physical properties

Hardness: 7 (Mohs scale), Color: Rusty brown to tan due to iron staining, Luster: Waxy to dull, Structure: Circular/donut-shaped central cavity (lumen) within a silicified matrix.

Formation & geological history

Formed during the Paleozoic era (likely Mississippian or Pennsylvanian periods) when crinoid sea lily stems were buried in ocean sediment and replaced by silica (chert) via permineralization.

Uses & applications

Primarily collected as geological specimens, used in folk jewelry (Hag stones or fairy stones), and used for educational purposes to study prehistoric marine life.

Geological facts

Crinoids are marine animals related to starfish and sea urchins. Their stems are made of stacked disk-like plates that often separate after death, leaving behind these 'bead' fossils.

Field identification & locations

Identified by the distinct circular or star-shaped hole in the center of a hard, rounded stone. Commonly found in riverbeds, gravel pits, and limestone-rich regions of the Midwest USA and UK.

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