sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale; Color: Light gray, white, yellowish, or tan; Luster: Earthy to sub-vitreous; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Hardness: 3 on the Mohs scale
Color: Light gray, white, yellowish, or tan
Luster: Earthy to sub-vitreous

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in marine environments. Geological age ranges from Precambrian to recent.

Uses & applications

Extensively used in construction as building stone, a primary component in the manufacture of Portland cement, agricultural soil conditioning, and metallurgical flux.

Geological facts

Limestone often contains fossils of ancient marine organisms, providing a rich record of Earth's evolutionary history. Famous landmarks like the Great Pyramids of Giza are built largely from limestone.

Field identification & locations

Easily identified by its characteristic fizz or effervescence when a drop of weak hydrochloric acid (or vinegar) is applied due to the release of carbon dioxide. Found worldwide in sedimentary basins.