sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite crystals; Specific Gravity: 2.5-2.7

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

Identified June 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through chemical precipitation from ocean water or cave environments. Found in vast sedimentary basins worldwide.

Uses & applications

Extensively used in construction as aggregate, cement production, glass making, and as a soil conditioner in agriculture. Pure forms are used in the chemical and pharmaceutical industries.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary parent material for karst landscapes, which include caves and sinkholes. The Great Pyramids of Giza are mostly constructed from limestone.

Field identification & locations

Identify in the field by checking for a reaction (fizzing) when a drop of dilute hydrochloric acid is applied. It is commonly found in areas that were once prehistoric shallow seas. Often contains visible fossils of marine organisms.