sedimentary
Coquina
Bioclastic Limestone
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
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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.
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