sedimentary
Fossiliferous Limestone with Crinoid Stem
Bioclastic Limestone (CaCO3)
Hardness: 3-4 on Mohs scale; Color: Grey to tan; Luster: Dull to earthy; Structure: Fine-grained matrix with visible circular fossil inclusions; Cleavage: None (conchoidal fracture)
- Hardness
- 3-4 on Mohs scale
- Color
- Grey to tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 on Mohs scale; Color: Grey to tan; Luster: Dull to earthy; Structure: Fine-grained matrix with visible circular fossil inclusions; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed in warm, shallow marine environments from the accumulation of calcium carbonate and skeletal remains of marine organisms. These specific fossils likely date from the Paleozoic era (Ordovician to Mississippian periods).
Uses & applications
Used in construction, as a building stone (limestone), for manufacturing lime and cement, and as educational specimens for fossil collectors.
Geological facts
The circular features are cross-sections of crinoid stems, also known as 'sea lilies,' which were marine animals related to starfish. Some locals call these fossil segments 'St. Cuthbert's beads'.
Field identification & locations
Identified by the presence of small, donut-shaped or coin-shaped fossils (columnals) embedded in a carbonate matrix. Common in areas with exposed Paleozoic bedrock like the Midwest and Appalachian regions of the US.
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