sedimentary

Limestone

Sedimentary Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Mohs hardness: 3; Color: Gray, tan, or yellowish-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.5-2.7

Hardness: 3
Color: Gray, tan, or yellowish-white
Luster: Dull to earthy

Identified June 5, 2026More sedimentary →

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Physical properties

Mohs hardness: 3; Color: Gray, tan, or yellowish-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); 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 or lake water.

Uses & applications

Extensively used in construction as an aggregate, cement production, and as a flux in steel making. Also used as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, which feature caves and sinkholes.

Field identification & locations

Identified in the field by its softness (can be scratched by a steel knife) and its reaction to dilute hydrochloric acid (effervescence). Commonly found in areas that were once prehistoric seafloors.