sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Structure: non-crystalline or clastic (contains fossil fragments); Specific gravity: 2.3 to 2.7.

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

Identified March 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 on the Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Structure: non-crystalline or clastic (contains fossil fragments); Specific gravity: 2.3 to 2.7.

Formation & geological history

Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Primary source of lime for cement; used in road construction, building materials, and as an agricultural soil conditioner.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Many famous structures, including the Great Pyramids of Giza, were built using limestone.

Field identification & locations

Identifiable in the field by its tendency to fizz (effervesce) when a drop of diluted hydrochloric acid is applied. It is commonly found in areas that were once prehistoric seafloors.