sedimentary

Limestone

Sedimentary Calcite (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, but usually massive in rock form; Specific Gravity: 2.7

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

Identified June 4, 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 through chemical precipitation from calcium carbonate-saturated water.

Uses & applications

Used extensively in construction as aggregate, road base, and raw material for cement and lime. Also used as a soil conditioner in agriculture and as a building stone.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, where it dissolves to form caves and sinkholes.

Field identification & locations

Identified in the field by its softness (can be scratched by a steel knife) and its strong effervescence (fizzing) when in contact with dilute hydrochloric acid. Commonly found in areas that were once prehistoric seabeds.