sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: light gray to white; Luster: dull to earthy; Texture: fine-grained with slight fossiliferous or particulate layering; Reacts vigorously with dilute hydrochloric acid.

Hardness: 3 (Mohs scale)
Color: light gray to white
Luster: dull to earthy

Identified July 7, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: light gray to white; Luster: dull to earthy; Texture: fine-grained with slight fossiliferous or particulate layering; Reacts vigorously with dilute hydrochloric acid.

Formation & geological history

Formed primarily in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water. These processes occur over millions of years.

Uses & applications

Extensively used as a building material, aggregate for concrete, in the production of cement, as a soil conditioner in agriculture, and as a feedstock in various chemical industries.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, leading to the formation of massive cave systems through dissolution.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper penny or steel) and its reaction to acid. It is commonly found in ancient seabed deposits and mountain ranges globally.