sedimentary
Fossiliferous Limestone
Limestone (CaCO3) with Crinoid/Bivalve fossils
Hardness: 3 (on Mohs scale); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Structure: Clastic or Biogenic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.3-2.7
- Hardness
- 3 (on Mohs scale)
- Color
- Tan, beige, or light brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (on Mohs scale); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Structure: Clastic or Biogenic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.3-2.7
Formation & geological history
Formed in shallow marine environments over millions of years through the accumulation and cementation of calcium carbonate shell fragments and skeletal remains. Most are from the Paleozoic or Mesozoic eras.
Uses & applications
Mainly used as a decorative collector's specimen, construction material (crushed stone), or in the production of cement and lime.
Geological facts
This specimen contains numerous small circular 'ossicles' or columnals, likely from Crinoids (sea lilies), which are marine animals related to starfish. Some limestones are composed almost entirely of these biological remains.
Field identification & locations
Identify in the field by looking for visible shell fragments and testing for a reaction (fizzing) with diluted hydrochloric acid. Commonly found in areas that were ancient seabed regions such as the Midwest US or Southern UK.
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