sedimentary
Crinoid Fossil in Chert
Crinoid (Class Crinoidea) in Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: light gray to off-white; Luster: dull to waxy; Structure: fragmented stem ossicles within a fine-grained silica matrix.
- Hardness
- 6
- Color
- light gray to off-white
- Luster
- dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: light gray to off-white; Luster: dull to waxy; Structure: fragmented stem ossicles within a fine-grained silica matrix.
Formation & geological history
Formed in marine environments during the Paleozoic era (approx. 250-500 million years ago) through the accumulation of calcium carbonate skeletons later replaced by silica (chertification).
Uses & applications
Primarily used for geological study, education, and as decorative items or collectibles.
Geological facts
Crinoids are known as 'sea lilies' and are actually animals related to starfish, not plants. Their fossilized stem segments are often called 'Indian beads' or 'St. Cuthbert's beads'.
Field identification & locations
Identify by looking for circular or star-shaped cross-sections and stacked disc structures. Commonly found in areas with limestone or chert deposits, particularly throughout the Midwestern United States and the UK.
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