sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Hexagonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.

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

Identified May 31, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Hexagonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.

Formation & geological history

Formed primarily in shallow, warm marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also form chemically through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction (building stone, aggregate), as a primary ingredient in cement and lime, and used in agriculture to neutralize soil acidity.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils that provide insights into prehistoric marine life.

Field identification & locations

Identify in the field by its tendency to effervesce (fizz) when in contact with dilute hydrochloric acid. It is commonly found in karst landscapes and coastal regions.