sedimentary

Coquina / Shelly Sandstone

Calcareous Sandstone / Coquina

AI-generated identification · may be incorrect

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 July 24, 2026More sedimentary →

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Physical properties

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.