sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, typically light gray, white, or tan in color, dull to earthy luster, fine-grained texture, and effervesces (fizzes) when exposed to hydrochloric acid.

Identified August 7, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, typically light gray, white, or tan in color, dull to earthy luster, fine-grained texture, and effervesces (fizzes) when exposed to hydrochloric acid.

Formation & geological history

Formed by the accumulation of skeletal fragments from marine organisms such as coral, algal, and foraminifera, or through the chemical precipitation of calcium carbonate from water in marine or lacustrine environments.

Uses & applications

Extensively used in construction as building material, crushed stone for road bases, as a main ingredient in the manufacturing of cement, and in agriculture to neutralize acidic soils.

Geological facts

Limestone often contains well-preserved fossils of ancient sea life and makes up about 10% of the total volume of all sedimentary rocks on Earth. Famous structures like the Great Pyramids of Giza were built largely from limestone blocks.

Field identification & locations

Easily identified in the field by its light color, fine-grained appearance, and distinct fizzing reaction when tested with a weak acid like vinegar or hydrochloric acid. Found worldwide in regions with ancient shallow marine histories.