sedimentary

Coquina or Fossiliferous Conglomerate

Bioclastic Rudstone (variable composition)

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 →

Explore Coquina or Fossiliferous Conglomerate in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Shale

Shale (clastic sedimentary rock)

sedimentary

Brown Sandstone (River Rock)

Arenite

sedimentary

Shale

Argillaceous sedimentary rock

sedimentary

Mudstone

Argillite / Siliciclastic sedimentary rock

sedimentary