sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale), Color: Cream/White, Luster: Dull to earthy, Crystal Structure: Trigonal (often microcrystalline)

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale), Color: Cream/White, Luster: Dull to earthy, Crystal Structure: Trigonal (often microcrystalline)

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. Can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction as an aggregate, a key ingredient in cement, an architectural stone, and as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is essential for the formation of caves through the process of dissolution by slightly acidic groundwater.

Field identification & locations

Identifiable in the field by its softness (can be scratched by a copper coin) and its strong effervescent reaction when exposed to dilute hydrochloric acid. It is found globally in large sedimentary basins.