sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness 3 on Mohs scale, typically gray to tan in color, dull to earthy luster, fine-grained to coarse crystal structure.

Identified October 25, 2026More sedimentary →

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Physical properties

Hardness 3 on Mohs scale, typically gray to tan in color, dull to earthy luster, fine-grained to coarse crystal structure.

Formed by the accumulation of organic skeletal fragments and chemical precipitation in shallow marine environments over millions of years.

Widely used in construction, cement production, agriculture for soil conditioning, and as a flux in steel manufacturing.

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

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