sedimentary

Limestone

Calcium Carbonate (CaCO3)

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

Identified October 24, 2026More sedimentary →

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Physical properties

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

Formed through the accumulation and compaction of organic remains like shells and coral in shallow marine environments over millions of years.

Widely used in the construction industry for producing cement and concrete, as well as in agriculture to neutralize acidic soils.

Limestone frequently contains well-preserved fossils and forms dramatic landscapes like caves and sinkholes through chemical weathering.

Identified easily by its characteristic fizz when exposed to dilute hydrochloric acid, commonly found in sedimentary basins 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)