sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: White, gray, beige; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None in rock form; Specific gravity: 2.5-2.7

Hardness: 3 (Mohs scale)
Color: White, gray, beige
Luster: Dull to earthy

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: White, gray, beige; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None in rock form; Specific gravity: 2.5-2.7

Formation & geological history

Formed in marine environments through 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 the construction industry as building stone, aggregate for concrete, and as a component in cement production. Also used in soil neutralization and as a source of lime.

Geological facts

Limestone covers about 10% of the Earth's land surface. Most caves are formed in limestone because it is soluble in slightly acidic rainwater.

Field identification & locations

Identify by its reaction (fizzing) when exposed to a weak acid like vinegar. Commonly found in areas that were once covered by ancient shallow seas. Collectors look for fossil content within the specimen.