sedimentary

Limestone

Calcite (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline in rock form); Cleavage: Perfect rhombohedral in calcite; Specific gravity: 2.7

Hardness: 3 on Mohs scale
Color: Grey, tan, or white
Luster: Dull to earthy

Identified April 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form by the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used extensively as a building material (cut stone), in the manufacture of cement, as a soil conditioner in agriculture, and as a raw material in the glass and chemical industries.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils that provide a record of ancient marine life.

Field identification & locations

Identify in the field by applying a drop of dilute hydrochloric acid; it will fizz (effervesce) vigorously. Often contains visible fossils or shell fragments. Found globally in areas that were once prehistoric sea beds.