sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3-4 (Mohs); Color: white to light grey; Luster: earthy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals; Specific Gravity: 2.5-2.7

Hardness: 3-4 (Mohs)
Color: white to light grey
Luster: earthy to dull

Identified June 20, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3-4 (Mohs); Color: white to light grey; Luster: earthy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals; Specific Gravity: 2.5-2.7

Formation & geological history

Formed primarily through the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. It can also be precipitates from calcium-rich groundwater.

Uses & applications

Extensively used as a building material, aggregate for concrete, manufacture of lime, soil conditioner in agriculture, and as a flux in steel making.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary indicator of ancient marine environments and often contains well-preserved fossils.

Field identification & locations

Identify in the field by its light color and characteristic effervescence (fizzing) when a drop of diluted hydrochloric acid is applied. Commonly found in karst landscapes and widespread sedimentary basins.