sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, grayish color, dull to earthy luster, and exhibits effervescence when exposed to weak acid.

Identified November 8, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, grayish color, dull to earthy luster, and exhibits effervescence when exposed to weak acid.

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

Extensively used in construction as building material, aggregate for roads, and in the manufacture of cement and lime.

Limestone often contains well-preserved fossils and forms dramatic landscapes known as karst topography, featuring caves and sinkholes.

Easily identified by its gray to tan color and strong fizzing reaction with 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)