sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale, Color: White, gray, yellow, or brown, Luster: Earthy to vitreous, Crystal structure: Trigonal (Calcite), Cleavage: Perfect rhombohedral, Specific gravity: 2.71

Identified July 28, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale, Color: White, gray, yellow, or brown, Luster: Earthy to vitreous, Crystal structure: Trigonal (Calcite), Cleavage: Perfect rhombohedral, Specific gravity: 2.71

Formation & geological history

Formed by the accumulation and compaction of organic remains like shells, coral, and algal debris, or through chemical precipitation of calcium carbonate from water in marine environments, often spanning millions of years from Paleozoic to Cenozoic eras.

Uses & applications

Extensively used in construction as building stone, as an aggregate for road bases, in the manufacturing of cement (Portland cement), as a soil conditioner in agriculture, and in metallurgy as a flux.

Geological facts

Limestone often contains well-preserved fossils of ancient marine organisms. Famous structures like the Great Pyramid of Giza were partially constructed using limestone blocks.

Field identification & locations

Can be easily identified in the field by its characteristic effervescence (fizzing) when exposed to weak hydrochloric acid (such as vinegar). Found worldwide in regions with ancient shallow sea beds.