sedimentary
Fossiliferous Limestone (Coquina)
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, white; Luster: Dull/Earthy; Structure: Clastic/Biogenic with visible shell fragments; Cleavage: None; Specific Gravity: 2.3-2.7
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, white
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, white; Luster: Dull/Earthy; Structure: Clastic/Biogenic with visible shell fragments; Cleavage: None; Specific Gravity: 2.3-2.7
Formation & geological history
Formed in shallow marine environments from the accumulation and lithification of organic debris like mollusk shells and coral fragments. These deposits can range from the Paleozoic era to the present day.
Uses & applications
Used primarily in building construction as a facade stone, in the production of cement, as lime for soil treatment, and as a decorative stone in landscaping.
Geological facts
The Castillo de San Marcos in Florida is famously built out of coquina (a type of fossiliferous limestone). Its soft texture allowed it to 'absorb' cannonballs rather than shattering.
Field identification & locations
Identify by looking for visible fossil remains and shell fragments embedded in a fine-grained matrix. It will react and fizz (effervesce) when exposed to a drop of dilute hydrochloric acid.
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