sedimentary

Fossiliferous Limestone (Coquina)

Biogenic Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

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

Identified April 3, 2026More sedimentary →

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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.