sedimentary

Fossiliferous Limestone (Coquina)

Biogenic Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Gray, tan, white; Luster: Dull/Earthy; Structure: Clastic/Biogenic with visible shell fragments; Cleavage: None; Specific Gravity: 2.3-2.7

Hardness: 3 on Mohs scale
Color: Gray, tan, white
Luster: Dull/Earthy

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray, tan, white; Luster: Dull/Earthy; Structure: Clastic/Biogenic with visible shell fragments; Cleavage: None; Specific Gravity: 2.3-2.7

Formation & geological history

Formed in shallow marine environments from the accumulation and lithification of organic debris like mollusk shells and coral fragments. These deposits can range from the Paleozoic era to the present day.

Uses & applications

Used primarily in building construction as a facade stone, in the production of cement, as lime for soil treatment, and as a decorative stone in landscaping.

Geological facts

The Castillo de San Marcos in Florida is famously built out of coquina (a type of fossiliferous limestone). Its soft texture allowed it to 'absorb' cannonballs rather than shattering.

Field identification & locations

Identify by looking for visible fossil remains and shell fragments embedded in a fine-grained matrix. It will react and fizz (effervesce) when exposed to a drop of dilute hydrochloric acid.