sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, typically white, gray, or tan in color, with an earthy to vitreous luster and fine-grained crystal structure.

Identified October 25, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, typically white, gray, or tan in color, with an earthy to vitreous luster and fine-grained crystal structure.

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

Extensively used in construction as building material, in the manufacture of cement, and as a soil conditioner in agriculture.

Limestone often contains well-preserved fossils of ancient marine organisms and forms spectacular cave systems through dissolution.

Easily identified by its characteristic fizz when tested with dilute hydrochloric acid; found worldwide 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)