sedimentary
Coquina or Coral Fossil
Biogenic Limestone (Calcite/Aragonite)
Hardness: 3 (Mohs scale); Color: Cream, tan, or white; Luster: Dull/Earthy; Structure: Clastic or amorphous; Pitted or 'brain-like' texture with small visible pores and shell fragments.
- Hardness
- 3 (Mohs scale)
- Color
- Cream, tan, or white
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream, tan, or white; Luster: Dull/Earthy; Structure: Clastic or amorphous; Pitted or 'brain-like' texture with small visible pores and shell fragments.
Formation & geological history
Formed in high-energy marine environments like beaches or reefs where shell fragments or coral debris accumulate and are cemented together by calcium carbonate over millions of years.
Uses & applications
Used in construction as a building material, in road beds, as a source of lime for agriculture, and for decorative landscape rock or garden accents.
Geological facts
Coquina is unique because it is often soft when first quarried but hardens significantly when exposed to air; historically, it was used to build forts (like Castillo de San Marcos) because it would absorb cannonballs rather than shattering.
Field identification & locations
Identify in the field by its porous, shell-like appearance and reactivity to weak acids (it will fizz). Commonly found along coastal regions, particularly in Florida, the Caribbean, and coastal Australia.
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