sedimentary
Coquina
Biogenic Limestone (Calcium Carbonate - CaCO3)
Hardness: 2-3 (Mohs scale); Color: Pale brown, tan, or gray; Luster: Dull/Earthy; Structure: Clastic/Biogenic, visible fragments of shells; Cleavage: None; Specific Gravity: 2.5-2.7
- Hardness
- 2-3 (Mohs scale)
- Color
- Pale brown, tan, or gray
- Luster
- Dull/Earthy
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Physical properties
Hardness: 2-3 (Mohs scale); Color: Pale brown, tan, or gray; Luster: Dull/Earthy; Structure: Clastic/Biogenic, visible fragments of shells; Cleavage: None; Specific Gravity: 2.5-2.7
Formation & geological history
Formed in high-energy marine environments where waves and currents accumulate large quantities of shell fragments. Over time, these fragments are cemented together by calcium carbonate. Most deposits are relatively young (Pleistocene to Holocene).
Uses & applications
Used historically as a building material (e.g., Castillo de San Marcos), as road base, and for landscaping or aquarium decoration.
Geological facts
Coquina was an ideal material for fortresses because its porous nature absorbed the impact of cannonballs rather than shattering, making it an extremely effective defensive barrier.
Field identification & locations
Identifiable by its 'cereal bar' or granola-like appearance, clearly composed of broken mollusk or coral fragments. It is most commonly found along the coastal regions of Florida and the Carolinas.
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