sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Grey, tan, or white with earthy tones; Luster: Dull to earthy; Texture: Fine to coarse grained, often contains visible fossil fragments or mineral grains; Cleavage: None (conchoidal or irregular fracture).

Hardness: 3 on Mohs scale
Color: Grey, tan, or white with earthy tones
Luster: Dull to earthy

Identified June 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. It can also form chemically through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used as a building material, in the manufacture of cement, as an aggregate for the base of roads, and as a soil conditioner in agriculture. Pure varieties are used in pharmaceutical and food products.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Most of the world's caves are formed in limestone because it is easily dissolved by acidic groundwater.

Field identification & locations

Identify in the field by checking for the presence of fossils and testing with a drop of weak acid (like vinegar); limestone will fizz (effervesce) as it releases carbon dioxide gas. Common in ancient reef environments and mountain ranges.