sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale. Color: Light grey, beige, or off-white. Luster: Dull to earthy. Texture: Fine-grained, microcrystalline to fossiliferous. Reacts strongly with diluted acid (effervesces).

Hardness: 3 on Mohs scale
Color: Light grey, beige, or off-white
Luster: Dull to earthy

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale. Color: Light grey, beige, or off-white. Luster: Dull to earthy. Texture: Fine-grained, microcrystalline to fossiliferous. Reacts strongly with diluted acid (effervesces).

Formation & geological history

Formed in shallow, warm marine waters by the accumulation of organic debris such as coral, shells, and fecal matter, as well as chemical precipitation of calcium carbonate over millions of years.

Uses & applications

Extensively used in construction as aggregate, building stone, and dimension stone, as well as a primary ingredient in cement and lime production, soil conditioner in agriculture, and industrial chemical applications.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. Famous geological structures like the White Cliffs of Dover and extensive cave systems with stalactites and stalagmites are composed of limestone.

Field identification & locations

Can be identified by its relative softness (scratched by a copper penny or steel nail), light chalky-grey appearance, and strong reaction (fizzing) when exposed to cold dilute hydrochloric acid or household vinegar.