sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale. Color: ranges from white, gray, yellow to black depending on impurities. Luster: earthy to vitreous. Crystal structure: hexagonal (calcite). Cleavage: rhombohedral. Specific gravity: 2.7 - 2.9

Hardness: 3 on Mohs scale
Luster: earthy to vitreous

Identified August 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by 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 varies widely from Precambrian to Recent.

Uses & applications

Widely used in construction (as building material and aggregate in road base), cement production, agriculture (soil conditioning), and metallurgical flux.

Geological facts

Limestone often contains fossils of ancient marine organisms, providing a window into Earth's prehistoric biosphere. Famous structures like the Great Pyramids of Giza were built largely from limestone.

Field identification & locations

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