sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: typically light gray, tan, or white; Luster: earthy to dull; Crystal structure: trigonal (calcite-based); Cleavage: rhombohedral (in crystalline form); Specific gravity: 2.7.

Hardness: 3 on Mohs scale
Color: typically light gray, tan, or white
Luster: earthy to dull

Identified May 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily 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

Extensively used as a building material, aggregate for concrete, raw material for cement, soil conditioner in agriculture, and a pigment in various industrial products.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type in which most of the world's caves are formed through the process of chemical weathering.

Field identification & locations

Identify in the field by its softness (scratchable with a copper penny) and its reaction to dilute hydrochloric acid (it will fizz or effervesce). Commonly found in areas that were once under shallow, warm seas.