sedimentary
Coquina or Fossiliferous Limestone
Fossiliferous Calcarenite (CaCO3)
Hardness: 3-4 (Mohs); Color: Dark grey to charcoal; Luster: Dull/Earthy; Crystal structure: Non-crystalline mass of cemented fossils; Cleavage: None; Specific Gravity: 2.3–2.7
- Hardness
- 3-4 (Mohs)
- Color
- Dark grey to charcoal
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: Dark grey to charcoal; Luster: Dull/Earthy; Crystal structure: Non-crystalline mass of cemented fossils; Cleavage: None; Specific Gravity: 2.3–2.7
Formation & geological history
Formed in marine environments (shallow seas or continental shelves) from the accumulation of organic debris, shells, and fossil fragments that are mechanically or chemically cemented over millions of years.
Uses & applications
Used in the production of cement and lime, as road base material, and occasionally in landscape architecture or as decorative garden stones.
Geological facts
This specimen appears to be packed with high-density fossil fragments, likely crinoids or shell hash. Coquina is unique because it is composed almost entirely of the skeletal remains of organisms.
Field identification & locations
Identify by looking for a 'pock-marked' or grainy appearance that reveals fossil outlines when viewed closely. Found globally in coastal areas or inland where ancient seabed’s once existed. Reacts with HCl acid.
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