sedimentary

Fossiliferous Limestone with Crinoid Stem

Bioclastic Limestone (CaCO3)

AI-generated identification · may be incorrect

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

Identified June 1, 2026More sedimentary →

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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.