sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3, typically white to light gray or tan in color, dull to earthy luster, and reacts with dilute hydrochloric acid.

Identified November 5, 2026More sedimentary →

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Physical properties

Mohs hardness of 3, typically white to light gray or tan in color, dull to earthy luster, and reacts with dilute hydrochloric acid.

Formed through the accumulation of skeletal fragments of marine organisms like coral, algal, and foraminifera in shallow marine environments.

Widely used in construction as building stone, aggregate in concrete, and for the production of lime and cement.

Limestone often contains well-preserved fossils and forms dramatic cave systems through chemical weathering by acidic groundwater.

Identified easily by its light color, relative softness, and effervescence when exposed to 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)