sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale. Color ranges from white, gray, yellow, to brown. Luster is earthy to sub-vitreous. Crystal structure is trigonal/hexagonal (calcite). Cleavage is perfect in three directions (rhombohedral). Specific gravity is 2.71.

Hardness: 3 on the Mohs scale

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed over millions of years through the accumulation and compaction of organic remains such as shells, coral, and algae, or through the chemical precipitation of calcium carbonate from water in marine environments.

Uses & applications

Widely used in the manufacture of cement, as a building material, road base, aggregate in concrete, soil conditioner in agriculture, and in the production of lime.

Geological facts

Limestone often contains fossils of ancient marine organisms since it forms in shallow marine waters. Famous structures like the Great Pyramids of Giza were partially constructed using limestone blocks.

Field identification & locations

Can be easily identified in the field by its characteristic reaction to dilute hydrochloric acid, producing effervescence (fizzing) due to the release of carbon dioxide.