sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness 3 on the Mohs scale, typically gray or tan in color, dull to earthy luster, and lacks a defined crystal structure.

Identified October 23, 2026More sedimentary →

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Physical properties

Hardness 3 on the Mohs scale, typically gray or tan in color, dull to earthy luster, and lacks a defined crystal structure.

Formed through the accumulation of shell, coral, algal, and fecal debris, often in shallow marine environments over millions of years.

Extensively used in construction as aggregate, in the production of cement, and in agriculture for neutralizing soil acidity.

Limestone frequently contains well-preserved fossils of ancient marine life and dissolves easily in acidic solutions, forming caves and sinkholes.

Identified easily by its characteristic fizz when a drop of weak hydrochloric acid is applied due to the release of carbon dioxide.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)