sedimentary
Coquina / Limonite-stained Limestone
Sedimentary Limestone with Iron Oxyhydroxide (FeO(OH)·nH2O)
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
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Physical properties
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
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.
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