sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Tan, buff, gray, orange-brown; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Rhombohedral (in mineral form).

Hardness: 3 on Mohs scale
Color: Tan, buff, gray, orange-brown
Luster: Dull/Earthy

Identified April 6, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Tan, buff, gray, orange-brown; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Rhombohedral (in mineral form).

Formation & geological history

Formed primarily from the accumulation of skeletal fragments of marine organisms such as coral, foraminifera, and mollusks in shallow marine environments over millions of years.

Uses & applications

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

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks on Earth. It is the primary parent rock for caves and karst topography because it is soluble in rainwater.

Field identification & locations

Identify in the field by its reaction to dilute hydrochloric acid (it will fizz). Look for fossil remains and a fine-grained, earthy texture. Common in ancient reef areas and basin regions.