sedimentary
Crinoid Stem Fossil in Matrix
Crinoid (Class Crinoidea) in Limestone/Siltstone matrix
Hardness: 3-4 (matrix/calcite). Color: Dark gray/black matrix with white/tan circular inclusions. Luster: Dull to waxy. Structure: Disk-shaped fossil cross-sections with central lumens (holes). Cleavage: Perfect rhombohedral in fossil segments.
- Hardness
- 3-4 (matrix/calcite)
- Color
- Dark gray/black matrix with white/tan circular inclusions
- Luster
- Dull to waxy
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Physical properties
Hardness: 3-4 (matrix/calcite). Color: Dark gray/black matrix with white/tan circular inclusions. Luster: Dull to waxy. Structure: Disk-shaped fossil cross-sections with central lumens (holes). Cleavage: Perfect rhombohedral in fossil segments.
Formation & geological history
Formed in shallow marine environments during the Paleozoic Era (approx. 250-500 million years ago) through the accumulation of skeletal remains on the ocean floor, followed by lithification.
Uses & applications
Primarily used as educational specimens, collectibles, and occasionally carved into jewelry or used as decorative inlay.
Geological facts
Crinoids are actually animals related to starfish and sea urchins, often called sea lilies. The circular shapes seen here are cross-sections of their columnal stems.
Field identification & locations
Identify by looking for the distinct 'cheerio' or star-shaped central canal within the circular segments. Found commonly in limestone outcrops, riverbeds, and Great Lakes beaches.
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