sedimentary

Coquina / Fossiliferous Limestone

Fossiliferous Calcarenite (Calcium carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: cream, tan, or grey; Luster: dull to earthy; Structure: clastic/biogenic with visible shell fragments and vugs (holes); Cleavage: none.

Hardness: 3-4 (Mohs scale)
Color: cream, tan, or grey
Luster: dull to earthy

Identified March 9, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: cream, tan, or grey; Luster: dull to earthy; Structure: clastic/biogenic with visible shell fragments and vugs (holes); Cleavage: none.

Formation & geological history

Formed in high-energy marine environments (beaches or shallow reefs) where shell fragments and coral debris accumulate. Over time, these are compacted and cemented by calcite. Many specimens date from the Pleistocene or Holocene epochs.

Uses & applications

Historically used as a building material for forts and colonial structures due to its shock-absorbent nature. Today used in construction gravel, landscaping, and as a calcium source in animal feed.

Geological facts

Famous for its role in the Spanish colonial architecture of Florida; the Castillo de San Marcos survived cannon fire because the soft, porous stone absorbed the impacts rather than shattering.

Field identification & locations

Identified by the presence of numerous small holes and visible shell fragments. In the field, look for 'honeycomb' textures on coastal outcrops. Common in Florida, North Carolina, and coastal Australia.