sedimentary

Coquina

Bioclastic Limestone

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: Cream, tan, or gray; Luster: Dull to earthy; Structure: Fragmental/Clastic; Cleavage: None (friable); Specific Gravity: 2.2-2.5

Hardness: 3 (Mohs scale)
Color: Cream, tan, or gray
Luster: Dull to earthy

Identified May 7, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: Cream, tan, or gray; Luster: Dull to earthy; Structure: Fragmental/Clastic; Cleavage: None (friable); Specific Gravity: 2.2-2.5

Formation & geological history

Formed in high-energy marine environments (beaches) through the accumulation and mechanical sorting of shell fragments and coral debris, typically from the Holocene or Pleistocene epochs.

Uses & applications

Used historically as building stone (notably in Florida), as aggregate for road beds, and as a calcium source in animal feed or architectural landscaping.

Geological facts

The Castillo de San Marcos in St. Augustine, Florida, was built from coquina; its porous nature allowed it to absorb cannonball impacts rather than shattering.

Field identification & locations

Easily identified by the visible presence of whole or broken sea shells loosely cemented together; commonly found along the coastal regions of Florida, Australia, and the United Kingdom.