sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: typically tan, gray, or beige; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.5-2.7

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

Identified June 29, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: typically tan, gray, or beige; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.5-2.7

Formation & geological history

Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from lake or ocean water.

Uses & applications

Extensively used in construction as an aggregate, architectural stone, cement manufacturing, and in agriculture to neutralize soil acidity.

Geological facts

Most limestones are skeletal in nature, meaning they are composed of the remains of ancient sea creatures. It is the primary rock type that forms karst landscapes, including most of the world's largest caves.

Field identification & locations

Identify in the field by checking for the presence of fossil fragments and its reaction to dilute hydrochloric acid (it will fizz). Commonly found in areas that were once prehistoric ocean floors.