sedimentary

Limestone

Calcium Carbonate (CaCO3)

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

Hardness: 3 on Mohs scale
Color: Tan, gray, or white
Luster: Dull to earthy

Identified May 23, 2026More sedimentary →

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Physical properties

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

Formation & geological history

Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from ocean water or cave water. Geological age ranges from Precambrian to modern-day.

Uses & applications

Extensively used in construction, road base, cement manufacturing, agriculture (soil conditioner), and as a chemical feedstock.

Geological facts

Limestone covers about 10% of the total surface area of the Earth's dry land. It is the primary rock type found in karst landscapes, which are characterized by caves and sinkholes.

Field identification & locations

Identify in the field by its softness (scratched by a copper penny or steel) and its reaction to cold dilute hydrochloric acid (it will effervesce/fizz). Commonly found in sedimentary basins and coastal regions.