sedimentary

Coquina / Limonite-stained Limestone

Sedimentary Limestone with Iron Oxyhydroxide (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Creamy white with yellowish-orange iron staining; Luster: Dull, earthy; Crystal Structure: Amorphous/microcrystalline; Cleavage: None/clastic; Specific Gravity: 2.3-2.7

Hardness: 3-4 (Mohs scale)
Color: Creamy white with yellowish-orange iron staining
Luster: Dull, earthy

Identified May 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and hardening of calcium carbonate shell fragments or coral in shallow marine environments, later stained by percolating iron-rich groundwater during the Holocene or Pleistocene epochs.

Uses & applications

Used primarily in construction for building stone, road base material, and decorative landscaping. Also used as a historical building material in coastal regions.

Geological facts

Many historic forts in Florida, such as Castillo de San Marcos, were built using similar stone because its porous nature absorbed cannonball impacts rather than shattering.

Field identification & locations

Identify in the field by checking for a reaction to dilute hydrochloric acid (fizzing) and looking for porous textures or visible organic debris. Commonly found in coastal areas and interior limestone quarries.