sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale. Color: Tan, yellowish-brown, light grey, or beige. Luster: Earthy, dull. Specific gravity: 2.5-2.7. Cleavage: Poor, irregular fracture. Texture: Microcrystalline to fine-grained, highly weathered and pitted surface.

Hardness: 3 on Mohs scale
Color: Tan, yellowish-brown, light grey, or beige
Luster: Earthy, dull

Identified July 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the accumulation of organic debris such as shell, coral, algal, and fecal debris in clear, warm, shallow marine waters, or by chemical precipitation of calcium carbonate from lake or ocean water over millions of years.

Uses & applications

Extensively used in construction as building stone, crushed stone for road base, aggregate in concrete, production of cement and lime, soil conditioning in agriculture, and neutralizer in chemical processes.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks worldwide. It reacts visibly by fizzing when exposed to cold dilute hydrochloric acid due to its calcite content.

Field identification & locations

Identified by its soft hardness (scratched easily by a steel nail), dull earthy luster, tan/grey color, and strong effervescence with weak acids. Commonly found in riverbeds, caves, quarries, and ancient marine basin deposits.