sedimentary
Fossilized Crinoid Stem Segment
Crinoid (Phylum Echinodermata, Class Crinoidea)
Hardness: 3 (calcite composition); Color: Tan, beige, or gray; Luster: Dull/earthy; Structure: Cylindrical or disk-like shape with a central hole (lumen); Specific gravity: Approx 2.7
- Hardness
- 3 (calcite composition)
- Color
- Tan, beige, or gray
- Luster
- Dull/earthy
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Physical properties
Hardness: 3 (calcite composition); Color: Tan, beige, or gray; Luster: Dull/earthy; Structure: Cylindrical or disk-like shape with a central hole (lumen); Specific gravity: Approx 2.7
Formation & geological history
Formed from the mineralized remains of marine animals related to starfish. These organic remains were buried in sediment in ancient shallow seas, often during the Paleozoic era (approx. 250-500 million years ago).
Uses & applications
Primarily used for educational study, amateur fossil collecting, and occasionally used as beads in folk jewelry (often called 'St. Cuthbert's beads').
Geological facts
Crinoids are known as 'sea lilies' because they resemble flowers, but they are actually animals. They are one of the oldest living fossil groups, appearing in the Ordovician period.
Field identification & locations
Identify by looking for perfect geometric circular or star-shaped cross-sections and stacked 'stack of coins' structure. Commonly found in limestone outcrops and gravel riverbeds in the Midwestern USA.
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