sedimentary

Limestone

Calcium Carbonate (CaCO3)

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

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

Widely used in construction as building stone, crushed stone for road base, and as a primary raw material in the manufacture of cement and lime.

Limestone often contains well-preserved fossils and can dissolve slightly in acidic water to form spectacular cave systems and karst topography.

Easily identified by its characteristic fizz when tested with dilute hydrochloric acid; 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)