sedimentary

Coquina Limestone (Fossiliferous Limestone)

Calcareous bioclastic sedimentary rock (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: tan, buff, or light grey; Luster: dull to earthy; Structure: poorly consolidated to cemented shells; Specific Gravity: 2.3–2.6.

Hardness: 3 (Mohs scale)
Color: tan, buff, or light grey
Luster: dull to earthy

Identified March 26, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: tan, buff, or light grey; Luster: dull to earthy; Structure: poorly consolidated to cemented shells; Specific Gravity: 2.3–2.6.

Formation & geological history

Formed in high-energy marine environments like shorelines where shell debris accumulates in thick deposits. Over time, chemical precipitates cement the organic fragments together. Most common in recent geological epochs like the Pleistocene.

Uses & applications

Used primarily in construction for building stone and road base material. Historically used for fortresses due to its ability to absorb cannon fire. Crushed into aggregate or used as a calcium source in agriculture.

Geological facts

The Castillo de San Marcos in Florida was built from coquina; the stone was so soft it absorbed cannonballs rather than shattering, making the fort nearly invincible for its time.

Field identification & locations

Identify by its coarse, 'oatmeal-like' texture of visible shell fragments. Found commonly along the coastal southeastern United States (especially Florida and the Carolinas) and other worldwide coastlines with high carbonate activity.