sedimentary

Coquina or Fossiliferous Sandstone

Fossiliferous Calcarenite (CaCO3 with SiO2 inclusions)

AI-generated identification · may be incorrect

Hardness: 3-4 (matrix) to 7 (quartz grains); Color: Tan, beige, grey; Luster: Dull/Earthy; Structure: Clastic with visible shell fragments and lithic inclusions; Specific Gravity: 2.3-2.6

Hardness: 3-4 (matrix) to 7 (quartz grains)
Color: Tan, beige, grey
Luster: Dull/Earthy

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (matrix) to 7 (quartz grains); Color: Tan, beige, grey; Luster: Dull/Earthy; Structure: Clastic with visible shell fragments and lithic inclusions; Specific Gravity: 2.3-2.6

Formation & geological history

Formed in high-energy marine shoreline or beach environments where shell fragments and mineral sediment accumulate and are cemented together by calcium carbonate over thousands to millions of years.

Uses & applications

Used historically as a building material (notably in Florida/Spain), as road base, or as aggregate for landscaping and erosion control.

Geological facts

This specimen contains a notable dark lithic clast (possibly basalt or chert) embedded in a lighter matrix of crushed shells and sand. It is often porous and can be quite lightweight compared to igneous rocks.

Field identification & locations

Identify by looking for visible shell bits and a gritty texture. It will typically react (fizz) when exposed to a weak acid like vinegar due to the calcium carbonate content. Common in coastal regions.