sedimentary
Coquina / Fossiliferous Limestone
Biogenic Limestone (Calcium Carbonate - CaCO3)
Hardness: 3-4 (Mohs scale); Color: Tan, brownish-orange, creamy white; Luster: Dull, earthy; Structure: Fragmental/Clastic containing fossil imprints; Cleavage: None; Specific Gravity: 2.3-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Tan, brownish-orange, creamy white
- Luster
- Dull, earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-4 (Mohs scale); Color: Tan, brownish-orange, creamy white; Luster: Dull, earthy; Structure: Fragmental/Clastic containing fossil imprints; Cleavage: None; Specific Gravity: 2.3-2.7
Formation & geological history
Formed in high-energy marine environments where shell fragments and marine debris accumulate and are naturally cemented by calcium carbonate (calcite). These specimens often date from the Cenozoic Era to the present.
Uses & applications
Used historically as a construction material for forts (like Castillo de San Marcos) and homes, as base material for roads, and as a decorative stone in landscaping and fossil collecting.
Geological facts
This specific piece is rich in gastropod (snail-like) and bivalve molds. In historic forts, coquina proved surprisingly effective against cannonballs because the porous rock would compress and absorb the impact rather than shattering.
Field identification & locations
Identify in the field by looking for a rock composed almost entirely of shells or shell molds (negative imprints). Frequently found in coastal regions, particularly Florida, North Carolina, and the Caribbean. It will fizz when exposed to weak acid (vinegar).
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary