sedimentary
Crinoid Stem Fossil (in Chert or Limestone Matrix)
Crinoidea (Class) - Calcium Carbonate (CaCO3)
Hardness: 3-4 (calcite) to 7 (if silicified); Color: Tan, grey, or off-white; Luster: Dull to earthy; Structure: Cylindrical segments with central 'pith' or hole; Cleavage: Rhombohedral (in fossil segments).
- Hardness
- 3-4 (calcite) to 7 (if silicified)
- Color
- Tan, grey, or off-white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (calcite) to 7 (if silicified); Color: Tan, grey, or off-white; Luster: Dull to earthy; Structure: Cylindrical segments with central 'pith' or hole; Cleavage: 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, later lithified into rock.
Uses & applications
Used primarily for educational purposes, paleontological study, lapidary work (when silicified), and as common collector items.
Geological facts
Crinoids are also known as 'Sea Lilies.' Despite their plant-like appearance, they are marine animals related to starfish and sea urchins. Their fossilized segments are often called 'Indian beads' or 'St. Cuthbert's beads.'
Field identification & locations
Identify by looking for stacked, disc-like buttons or small star-shaped holes in cross-sections. Commonly found in limestone quarries, creek beds, and road cuts in the Midwestern US and UK.
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