sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3; color ranges from white, gray, to yellow; dull to earthy luster; trigonal crystal system; excellent cleavage.

Identified November 7, 2026More sedimentary →

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Physical properties

Mohs hardness of 3; color ranges from white, gray, to yellow; dull to earthy luster; trigonal crystal system; excellent cleavage.

Formed by the accumulation of organic remains like shells and coral, or chemical precipitation in marine environments over millions of years.

Widely used in construction as aggregate, in cement manufacturing, as a soil conditioner in agriculture, and in metallurgy.

Limestone frequently contains well-preserved fossils and dissolves slowly in acidic water, creating extensive cave systems and karst topography.

Easily identified by its characteristic fizz when exposed to dilute hydrochloric acid; found globally in shallow marine 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)