sedimentary

Coquina

Biogenic Limestone (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly cemented fragments of shells and coral, Specific Gravity: 2.3-2.6

Identified March 14, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale), Color: tan, cream, or light brown, Luster: dull to earthy, Structure: poorly cemented fragments of shells and coral, Specific Gravity: 2.3-2.6

Formation & geological history

Formed in high-energy marine environments (beaches or near-shore) where shell fragments accumulate and are loosely cemented together by calcite; typically Holocene or Pleistocene in age.

Uses & applications

Used primarily in construction (building stone, road base), landscaping, and as a natural source of calcium carbonate for agricultural use.

Geological facts

Famous for its use in the construction of the Castillo de San Marcos in Florida; it is a 'soft' rock that was paradoxically resistant to cannon fire because it absorbed the impact instead of shattering.

Field identification & locations

Identify by its 'granola bar' appearance made of visible shell fragments; commonly found in coastal areas of Florida and North Carolina. Collectors look for well-preserved whole shells within the matrix.