sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: White, grey, or tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Specific Gravity: 2.5-2.7

Hardness: 3-4 (Mohs)
Color: White, grey, or tan
Luster: Dull/Earthy

Identified May 23, 2026More sedimentary →

Explore Limestone in the encyclopedia →

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, grey, or tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Specific Gravity: 2.5-2.7

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters over millions of years.

Uses & applications

Used extensively in construction (road base, concrete), agriculture (soil conditioner), and industrial manufacturing of glass and steel.

Geological facts

Limestone is the source of approximately 10% of the world's sedimentary rocks. It is also the primary material found in famous locations like the Great Pyramids and the White House.

Field identification & locations

Identify in the field by its reaction to dilute hydrochloric acid (effervescence) and its ability to be scratched by a steel blade. Found in abundant quantities globally.