sedimentary
Coquina (Limestone)
Bioclastic Limestone (CaCO3)
Hardness: 3 (Mohs scale), Color: Cream, tan, or white, Luster: Dull/Earthy, Crystal Structure: Amorphous/Biogenic, Porous and friable texture
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Physical properties
Hardness: 3 (Mohs scale), Color: Cream, tan, or white, Luster: Dull/Earthy, Crystal Structure: Amorphous/Biogenic, Porous and friable texture
Formation & geological history
Formed in high-energy marine environments (beaches/reefs) by the accumulation and mechanical sorting of shell fragments and coral debris, typically from the Holocene or Pleistocene epochs.
Uses & applications
Used as a historical building material (source of lime), in road construction, landscaping, and as a natural aquarium filter due to high calcium content.
Geological facts
The Castillo de San Marcos in Florida is famously built from coquina; its porous nature allowed it to absorb cannonball impacts rather than shattering.
Field identification & locations
Identify by visible shell fragments, high porosity, and strong effervescence when exposed to dilute hydrochloric acid. Commonly found along coastal areas with significant molluscan life.
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