sedimentary
Crinoid Stem Fossil
Class Crinoidea (Phylum Echinodermata), primarily Calcium Carbonate (CaCO3)
Hardness: 3 (Calcite); Color: Tan, gray, or white; Luster: Dull to earthy (unless replaced by quartz); Crystal structure: Typically hexagonal or circular cross-sections showing a central canal (lumen); Cleavage: Rhombohedral when calcite crystals are large.
- Hardness
- 3 (Calcite)
- Color
- Tan, gray, or white
- Luster
- Dull to earthy (unless replaced by quartz)
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Physical properties
Hardness: 3 (Calcite); Color: Tan, gray, or white; Luster: Dull to earthy (unless replaced by quartz); Crystal structure: Typically hexagonal or circular cross-sections showing a central canal (lumen); Cleavage: Rhombohedral when calcite crystals are large.
Formation & geological history
Formed through the fossilization of marine organisms known as 'sea lilies.' Most specimens date from the Paleozoic Era (541–252 million years ago) in shallow-water marine environments. The soft tissue decayed, leaving behind stacked calcified disks (columnals) that were buried in sediment.
Uses & applications
Used primarily as decorative items, educational specimens in paleontology, and occasionally in the creation of unique jewelry (sometimes called 'Indian beads'). Historically used by Native Americans as beads.
Geological facts
Crinoids are actually animals related to starfish and sea urchins, not plants. They have existed for over 500 million years and some species still live in the deep ocean today. When these stems break apart, the individual circular pieces are often called 'Saint Cuthbert's beads.'
Field identification & locations
Identified in the field by their distinct 'stacked coin' or 'bolt' appearance with ridged edges. Commonly found in limestone outcrops, riverbeds, and quarries across the Midwestern United States (Mississippian and Pennsylvanian age rocks) and the UK.
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