<p>Coquina from the Quaternary of Florida, USA
</p><p>This is a distinctive variety of fossiliferous limestone called coquina.  It is composed of finely-busted up seashells, typically clam shells &amp; snail shells (bivalves &amp; 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.
</p><p>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.
</p><p>Stratigraphy: Anastasia Formation, Upper Pleistocene to Holocene
</p>
Locality: unrecorded/undisclosed site at or near St. Augustine, northern part of the Atlantic Coast of Florida, USA
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/49135985766/">Coquina (Anastasia Formation, Quaternary; St. Augustine, Florida, USA) 2</a>