sedimentary

Limestone

Limestone (Calcium Carbonate, CaCO3)

Hardness: 3 on the Mohs scale. Color: Typically white, gray, tan, or yellow. Luster: Dull to earthy. Crystal structure: Trigonal (as calcite). Cleavage: Perfect rhombohedral cleavage. Specific gravity: 2.7 - 2.9.

Hardness: 3 on the Mohs scale
Color: Typically white, gray, tan, or yellow
Luster: Dull to earthy

Identified August 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, or through the chemical precipitation of calcium carbonate from water. Found globally in marine sedimentary basins.

Uses & applications

Widely used in construction as building stone, as an aggregate for roads, in the manufacturing of cement (portland cement), as a soil conditioner in agriculture, and in the production of lime.

Geological facts

Many of the world's most famous natural wonders, such as the white cliffs of Dover and vast cave systems, are composed almost entirely of limestone. It often contains well-preserved fossils.

Field identification & locations

Can be easily identified in the field by its characteristic reaction to dilute hydrochloric acid, which causes it to fizz violently due to the release of carbon dioxide gas. Found extensively in riverbeds, quarries, and coastal regions.