sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Tan, beige, or grey; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None in rock form; Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Tan, beige, or grey
Luster: Dull to earthy

Identified May 5, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Tan, beige, or grey; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None in rock form; Specific Gravity: 2.5-2.7

Formation & geological history

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

Uses & applications

Used primarily in construction (crushed stone, cement), as an architectural material, in glass making, and for soil treatment in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It is the primary stone used in the construction of the Great Pyramids of Giza.

Field identification & locations

Identify in the field by applying a drop of dilute hydrochloric acid; it will effervesce (fizz) vigorously. It is commonly found in regions that were once ancient sea beds, such as the Midwestern United States and Central Europe.