sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, typically beige, gray, or white in color, with a dull to sub-vitreous luster and fine-grained crystal structure.

Identified November 6, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, typically beige, gray, or white in color, with a dull to sub-vitreous luster and fine-grained crystal structure.

Formed from the accumulation of skeletal fragments like coral, algal, and mollusk shells over millions of years in shallow marine environments.

Widely used in construction as building material, crushed stone for road base, and as the primary raw material for manufacturing Portland cement.

Limestone often contains well-preserved fossils and can dissolve slowly in acidic water, creating fascinating cave systems and karst topography.

Identified easily by its characteristic fizz when a drop of weak hydrochloric acid is applied 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)