sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: cream, tan, or yellowish-brown; Luster: dull to earthy; Texture: clastic or non-clastic grain structure; Cleavage: none in rock form, rhombohedral in calcite crystals; Specific Gravity: 2.3-2.7

Hardness: 3 (Mohs scale)
Color: cream, tan, or yellowish-brown
Luster: dull to earthy

Identified April 15, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed primarily in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from calcium-rich waters in caves or springs.

Uses & applications

Extensively used in construction as building stone, road base, and a key ingredient in cement/concrete. Also used as a soil conditioner and in the production of lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Most cave systems in the world are formed in limestone because it is easily dissolved by acidic groundwater.

Field identification & locations

Identify in the field by testing with a drop of cold dilute hydrochloric acid; it will effervesce (fizz) vigorously. It is commonly found in ancient seabed deposits and mountainous regions.