sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, colors range from white to gray and tan, dull to earthy luster, and reacts strongly with dilute hydrochloric acid.

Identified November 9, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, colors range from white to gray and tan, dull to earthy luster, and reacts strongly with dilute hydrochloric acid.

Formed through the accumulation of organic remains like shells and coral, or chemical precipitation in marine environments over millions of years.

Widely used in construction as crushed stone for road base, aggregate in concrete, production of cement, and in agricultural soil treatment.

Limestone frequently contains well-preserved fossils and forms dramatic landscapes featuring caves, sinkholes, and karst topography.

Identified by its relatively soft nature, light coloration, and characteristic fizz when exposed to acid; found globally in sedimentary basins.

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)