sedimentary
Crinoid Stem Fragment
Crinoid (Phylum Echinodermata, Class Crinoidea)
Hardness: 3 (Calcite-based); Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (internal crystalline calcite); Cleavage: Perfect rhombohedral in individual ossicles; Specific gravity: Approx 2.7.
- Hardness
- 3 (Calcite-based)
- Color
- Gray, tan, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Calcite-based); Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (internal crystalline calcite); Cleavage: Perfect rhombohedral in individual ossicles; Specific gravity: Approx 2.7.
Formation & geological history
Formed through the organic accumulation and fossilization of marine arthropod stems. These specimens lived in shallow seas during the Paleozoic era (approx. 250-500 million years ago) and were buried in marine sediments.
Uses & applications
Used primarily in education, fossil collecting, and occasionally as decorative beads in jewelry known as 'St. Cuthbert's beads'. Can also be a component of 'encrinal limestone' used in construction.
Geological facts
Crinoids are known as 'sea lilies' because of their plant-like appearance, but they were actually animals. They are still alive today in deep ocean environments, though they were much more abundant in the prehistoric past.
Field identification & locations
Identify in the field by their cylindrical shape and clear central hole (lumen) or star/circle patterns on the ends. They are commonly found in limestone outcrops, riverbeds, and gravel pits across North America and Europe.
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