sedimentary
Fossiliferous Limestone (Coquina)
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3 (Mohs scale); Color: Gray, tan, or brownish; Luster: Dull/Earthy; Crystal Structure: Amorphous/Microcrystalline; High reactivity to dilute hydrochloric acid.
- Hardness
- 3 (Mohs scale)
- Color
- Gray, tan, or brownish
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Gray, tan, or brownish; Luster: Dull/Earthy; Crystal Structure: Amorphous/Microcrystalline; High reactivity to dilute hydrochloric acid.
Formation & geological history
Formed in marine environments through the accumulation of organic debris such as shell fragments, coral, and algae. Over millions of years, compaction and cementation (lithification) transform these bio-sediments into solid rock.
Uses & applications
Used primarily in construction as a building stone or road aggregate; also used in the manufacture of cement and lime, and as an educational specimen in paleontology.
Geological facts
This specimen contains numerous visible brachiopod or bivalve shell impressions. It serves as a record of ancient marine life and can be used by geologists to determine the age and paleoenvironment of the rock layer.
Field identification & locations
Identify in the field by looking for visible shell fragments and testing for effervescence with acid. Commonly found in areas that were once ancient sea beds, such as the Midwestern United States or the Jurassic Coast in the UK.
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