coquina

Coquina is a sedimentary rock formed from the accumulated shells and shell fragments of marine organisms, cemented together by calcium carbonate. It is a bioclastic limestone, typically light in color and characterized by a conspicuously porous, loosely consolidated texture. The name comes from the Spanish term coquina, meaning “shell,” reflecting its shell-rich composition.

Coquina forms in shallow, storm- and wave-driven coastal environments where abundant shelly debris is deposited. Over time, the loose fragments are lithified by minerals precipitating from seawater, producing a rock that remains relatively porous and softer than many other limestones. Its porosity and low density are notable properties, and fresh coquina can be comparatively easy to cut with hand tools, though cementation makes it durable enough for structural use when set in lime mortar.

Historically, coquina has been used as a building material in the Americas, especially in Florida and the Caribbean. It played a prominent role in colonial construction, including fortifications and public buildings, because its porosity allowed it to absorb and release moisture and it could be quarried locally. A well-known example is its use in the Castillo de San Marcos in St. Augustine, Florida. Today, coquina remains a recognized type of limestone, valued for its distinctive texture and historical associations, though modern construction uses are limited to preservation projects and specialty applications.