sedimentary
Coquina / Shelly Sandstone
Calcareous Sandstone / Coquina
Mohs hardness around 3-6 (variable depending on mineral content and shell fragments). Granular, porous texture composed of sand grains, small shell fragments, and calcium carbonate cement. Color ranges from light tan and grey to brownish dark grey. Dull, earthy to vitreous luster.
Identified More sedimentary →
Explore Coquina / Shelly Sandstone in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness around 3-6 (variable depending on mineral content and shell fragments). Granular, porous texture composed of sand grains, small shell fragments, and calcium carbonate cement. Color ranges from light tan and grey to brownish dark grey. Dull, earthy to vitreous luster.
Formation & geological history
Formed in shallow marine, beach, or nearshore environments where sand, quartz grains, shell debris, and organic fragments accumulate and become cemented by dissolved calcite or silica over time.
Uses & applications
Used locally as low-grade building stone, road fill, decorative landscaping gravel, or studied in geology as sedimentary indicator of ancient coastal environments.
Geological facts
Sedimentary rocks containing shell fragments and sand grains often preserve micro-fossils and offer clues about ancient shorelines and ocean currents.
Field identification & locations
Identified by its rough, sandy texture, visible mineral or shell grains, and soft friable nature. Common along coastal beaches, stream beds, and sedimentary rock formations worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary