sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale. Color: Varies widely, commonly white, gray, tan, or yellowish. Luster: Earthy to dull. Crystal structure: Trigonal (as calcite). Cleavage: Perfect rhombohedral cleavage in pure calcite crystals. Specific Gravity: 2.7 to 2.9.

Hardness: 3 on the Mohs scale
Color: Varies widely, commonly white, gray, tan, or yellowish
Luster: Earthy to dull

Identified July 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed mainly from the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, typically in shallow marine environments over millions of years.

Uses & applications

Widely used in construction as building material, an aggregate for roads, as a primary component of portland cement, and in agriculture to neutralize acidic soil.

Geological facts

Limestone formations often contain fossils, providing a rich record of Earth's ancient marine life and historical climate conditions.

Field identification & locations

Can be easily identified in the field by applying a drop of dilute hydrochloric acid, which causes it to fizz or effervesce due to the release of carbon dioxide gas. Found globally in regions with ancient marine deposition.