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 with hydrochloric acid.

Identified November 2, 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 with hydrochloric acid.

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

Widely used in construction as building stone, aggregate in concrete, and in the production of cement and agriculture lime.

Limestone frequently contains well-preserved fossils of ancient marine organisms and can form dramatic karst landscapes with caves and sinkholes.

Identified easily by its characteristic reaction to acid fizzing and relatively soft composition, found extensively worldwide.

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)