sedimentary
Fossiliferous Limestone
Fossiliferous Limestone (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, or reddish-brown from iron staining; Luster: Dull to earthy; Structure: Clastic or biogenic with visible shell fragments and brachiopod fossils; Cleavage: None (fractures roughly).
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, or reddish-brown from iron staining
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, or reddish-brown from iron staining; Luster: Dull to earthy; Structure: Clastic or biogenic with visible shell fragments and brachiopod fossils; Cleavage: None (fractures roughly).
Formation & geological history
Formed in shallow, calm marine environments where organic debris like shells and coral accumulate on the seafloor and are cemented together by calcium carbonate over millions of years, typically during the Paleozoic era.
Uses & applications
Used primarily in construction as crushed stone, for making cement, as a decorative stone in landscaping, and as educational specimens for paleontology.
Geological facts
This specimen contains abundant brachiopod and likely crinoid fragments, indicating it was part of a prehistoric seafloor. Brachiopods have existed for over 500 million years.
Field identification & locations
Identify by looking for visible shell imprints and its reaction (fizzing) to dilute hydrochloric acid. It is commonly found in areas with exposed sedimentary bedrock like the Midwest US and UK.
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