sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3, colors range from white to gray and tan, dull to earthy luster, and it reacts vigorously with dilute hydrochloric acid.

Identified November 8, 2026More sedimentary →

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Physical properties

Mohs hardness of 3, colors range from white to gray and tan, dull to earthy luster, and it reacts vigorously with dilute hydrochloric acid.

Formed through the accumulation of shell, coral, algal, and fecal debris, or by chemical precipitation of calcium carbonate from water.

Widely used in construction as building stone, aggregate in concrete, raw material for cement, and in agriculture for soil conditioning.

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

Identify in the field by its characteristic gray color, reactive effervescence with acid, and occasional fossil inclusions.

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)