sedimentary

Limestone

Calcium Carbonate (CaCO3)

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

Identified October 18, 2026More sedimentary →

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Physical properties

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

Formed through the accumulation of skeletal fragments, coral, algal, and fecal debris, often in shallow marine environments over millions of years.

Widely used in construction as building stone, aggregate in concrete, and for manufacturing cement, lime, and steel.

Limestone frequently contains well-preserved fossils and forms dramatic landscapes like caves and sinkholes due to its solubility in acidic water.

Easily identified by its reaction to dilute hydrochloric acid, producing carbon dioxide fizz. Found globally 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)