sedimentary
Fossilized Crinoid Stem
Class Crinoidea (Echinodermata)
AI-generated identification · may be incorrectHardness: 3 (calcite composition). Color: Grey, tan, or white. Luster: Dull to vitreous. Structure: Cylindrical or disc-like segments (columnals) often with a central hole (lumen). Cleavage: Rhombohedral (on individual calcite crystals).
- Hardness
- 3 (calcite composition)
- Color
- Grey, tan, or white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 3 (calcite composition). Color: Grey, tan, or white. Luster: Dull to vitreous. Structure: Cylindrical or disc-like segments (columnals) often with a central hole (lumen). Cleavage: Rhombohedral (on individual calcite crystals).
Formation & geological history
Formed through the permineralization of marine organisms. These 'sea lilies' were abundant in shallow seas during the Paleozoic era (541 to 252 million years ago), where their segmented stems were buried in calcium-rich sediment.
Uses & applications
Primarily used as educational specimens, biological indicators for dating rock layers, and for mineral collecting. Historically, individual segments were used as beads (sometimes called 'St. Cuthbert's beads').
Geological facts
Crinoids are animals related to starfish and sea urchins, not plants. While most species are extinct, some 'living fossils' still exist in deep oceans today. In the UK, they are famously known as 'star stones' or 'fairy money'.
Field identification & locations
Identify in the field by the distinct 'stacked' appearance of tiny discs or gears. They are extremely common in limestone regions, particularly in the Midwestern United States (like Indiana) and parts of Northern England.
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