sedimentary

Coquina or Fossiliferous Conglomerate

Bioclastic Rudstone (variable composition)

AI-generated identification · may be incorrect

Hardness: 3-7 (variable based on matrix/inclusion); Color: Brown, tan, and white; Luster: Dull/earthy matrix with pearly shell fragments; Structure: Coarse-grained, clastic; Cleavage: None (fractures around grains).

Hardness: 3-7 (variable based on matrix/inclusion)
Color: Brown, tan, and white
Luster: Dull/earthy matrix with pearly shell fragments

Identified July 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy marine or coastal environments where shell fragments and pebbles are rapidly buried and cemented by calcium carbonate (calcite) or iron oxide. Typical of the Holocene to Pleistocene epochs.

Uses & applications

Mostly used as a decorative landscaping stone, a collector's specimen for paleontology enthusiasts, or historically as a building material in coastal regions.

Geological facts

Famous structures like the Castillo de San Marcos in Florida were built from similar coquina rock, which was effective because its porous nature could absorb the shock of cannonballs without shattering.

Field identification & locations

Identify by looking for visible shell fragments and smooth pebbles cemented in a sandy or dark matrix. Common on beaches in Florida, the Carolinas, and along the Gulf Coast.