sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Texture: fine to coarse grained; Cleavage: none; Specific Gravity: 2.71.

Hardness: 3 on Mohs scale
Color: typically white, gray, or tan
Luster: dull to earthy

Identified March 31, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Texture: fine to coarse grained; Cleavage: none; Specific Gravity: 2.71.

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 precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used extensively in construction as building stone, road base, and a key ingredient in cement/concrete. Also used in agriculture to neutralize soil acidity.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the world's great cave systems, like Mammoth Cave, are carved out of limestone by acidic groundwater.

Field identification & locations

Can be identified in the field by its softness (scratched by a copper penny) and its strong Fizzing (effervescence) when exposed to a drop of dilute hydrochloric acid. It is found globally in sedimentary basins.