sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale, Color: Beige, tan, light brown, Luster: Earthy to dull, Crystal Structure: Hexagonal (calcite), Cleavage: Perfect rhombohedral, Specific Gravity: 2.71

Identified July 29, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale, Color: Beige, tan, light brown, Luster: Earthy to dull, Crystal Structure: Hexagonal (calcite), Cleavage: Perfect rhombohedral, Specific Gravity: 2.71

Formation & geological history

Formed by the accumulation and compaction of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in shallow marine environments.

Uses & applications

Widely used in the construction industry as building stone and aggregate, in the manufacture of cement, as a soil conditioner in agriculture, and in the production of lime.

Geological facts

Limestone formations often contain well-preserved fossils of ancient marine organisms and can dissolve slightly in acidic water, creating fascinating cave systems and karst topography.

Field identification & locations

Can be easily identified in the field by its characteristic reaction to dilute hydrochloric acid, which causes it to fizz and effervesce due to the release of carbon dioxide.