Crinoid Fossil Stem Segment

Physical Properties

Hardness: 3 (calcite); Color: Tan, grey, or white; Luster: Dull to earthy; Structure: Cylindrical or disc-shaped segmented ossicles; Cleavage: Rhombohedral (in individual calcite crystals).

Formation & Geological History

Formed from the skeletal remains of marine animals known as sea lilies. These animals lived in shallow seas from the Ordovician period (~485 million years ago) to the present, though fossil stems are most abundant in Paleozoic limestone.

Uses & Applications

Primarily used for geological education, fossil collecting, and occasionally drilled for use as beads in jewelry ('St. Cuthbert's beads').

Geological Facts

Crinoids are animals related to starfish and sea urchins, not plants. Their stems are made of stacked 'buttons' or ossicles that often fall apart, but are frequently preserved in large numbers in rock layers known as crinoidal limestone.

Field Identification & Locations

Identify by looking for stacked cylindrical segments or 'screw-like' threads on the side. Common in limestone outcrops, riverbeds, and quarries across the Midwest USA, UK, and Europe.

Identified on: 5/2/2026

Mode: Standard