sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: tan, grey, or white; Luster: dull; Crystal Structure: trigonal (when crystalline); Cleavage: rhombohedral; Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: tan, grey, or white
Luster: dull

Identified May 17, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: tan, grey, or white; Luster: dull; Crystal Structure: trigonal (when crystalline); Cleavage: rhombohedral; 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 be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used primarily in construction for building stone and road base, in the production of cement, as a decorative stone, and as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most caves, such as Mammoth Cave in Kentucky, are formed by the dissolution of limestone by acidic groundwater.

Field identification & locations

Identify in the field by its reaction to dilute hydrochloric acid (it will fizz) and its tendency to contain marine fossils. Common in areas that were once ancient seabeds.