sedimentary
Crinoid Fossil Stem Segment
Class Crinoidea (Echinodermata)
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).
- Hardness
- 3 (calcite)
- Color
- Tan, grey, or white
- Luster
- Dull to earthy
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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.
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