sedimentary

Limestone

Calcareous sedimentary rock (CaCO3)

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

Identified November 2, 2026More sedimentary →

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Physical properties

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

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

Widely used in construction as aggregate, in the production of cement, for agricultural soil conditioning, and as a dimension stone.

Limestone frequently contains well-preserved fossils and dissolves in acidic water, creating spectacular karst landscapes and cave systems.

Easily identified by its characteristic fizz when tested with dilute hydrochloric acid; found globally in sedimentary basins and ancient sea beds.

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)