Coquina from the Quaternary of Florida, USA

This is a distinctive variety of fossiliferous limestone called coquina. It is composed of finely-busted up seashells, typically clam shells & snail shells (bivalves & gastropods). Coquinas have high porosity - a significant amount of empty space exists between the grains. This results in coquina having a spongy appearance. Many samples are mixed with quartzose sand.

Coquina had military significance in early American history. Some military forts in Florida were constructed with coquina walls. The coquina essentially absorbed any cannonballs that were shot at the walls.

Stratigraphy: Anastasia Formation, Upper Pleistocene to Holocene