sedimentary

Coquina

Coquina (Bioclastic Limestone)

AI-generated identification · may be incorrect

Hardness: 2-3 (Mohs scale), Color: tan, cream, or light brown, Luster: earthy to pearly, Structure: clastic (fragmental), Cleavage: none, Specific Gravity: 2.2-2.4

Identified May 19, 2026More sedimentary →

Explore Coquina in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 2-3 (Mohs scale), Color: tan, cream, or light brown, Luster: earthy to pearly, Structure: clastic (fragmental), Cleavage: none, Specific Gravity: 2.2-2.4

Formation & geological history

Formed in high-energy marine environments where waves break and accumulate shell fragments. They are typically of Holocene to Pleistocene age (within the last 2.5 million years) and occur in coastal zones.

Uses & applications

Historically used as a building stone (notably in Florida and the Caribbean) because it is soft enough to quarry but hardens with exposure. Also used for road base and landscaping.

Geological facts

A famous example of Coquina architecture is the Castillo de San Marcos in St. Augustine, Florida. It is effectively a 'natural concrete' made entirely of fossilized shell debris.

Field identification & locations

Identify by looking for a mass of poorly cemented, coarse shell fragments with visible voids between them. Common in coastal areas like Florida, the Outer Banks, and shark teeth-rich deposits.