sedimentary
Coquina
Biogenic calcarenite / Coquina (CaCO3)
AI-generated identification · may be incorrectHardness: 3 (Mohs scale); Color: Cream, tan, or grey; Luster: Dull/Earthy; Structure: Clastic fossiliferous; Cleavage: None; Porosity: High.
- Hardness
- 3 (Mohs scale)
- Color
- Cream, tan, or grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream, tan, or grey; Luster: Dull/Earthy; Structure: Clastic fossiliferous; Cleavage: None; Porosity: High.
Formation & geological history
Formed in high-energy marine environments where shell fragments accumulate and are cemented together by calcium carbonate. Most deposits are relatively young (Pleistocene to Holocene).
Uses & applications
Used as building stone, especially in historical coastal fortifications like the Castillo de San Marcos, and as road base material.
Geological facts
The word 'coquina' is Spanish for 'small shells'. It is famous for being 'soft' enough to absorb cannonball impacts rather than shattering, making it a superior material for historic forts.
Field identification & locations
Commonly found along coastal areas in Florida, North Carolina, and Australia. Identified by the visible, often loosely cemented fragments of shells and coral.
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