sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness 3 on Mohs scale; color ranges from white, gray, to tan; dull to earthy luster; fine-grained crystal structure.

Identified October 25, 2026More sedimentary →

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Physical properties

Hardness 3 on Mohs scale; color ranges from white, gray, to tan; dull to earthy luster; fine-grained crystal structure.

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

Widely used in construction, cement production, agriculture to neutralize acidic soils, and as a flux in steel manufacturing.

Limestone frequently contains well-preserved fossils and forms famous geological features like caves via dissolution by acidic groundwater.

Identified easily by a vigorous fizz when tested with dilute hydrochloric acid. Found worldwide in 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)