sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Cream, tan, or light gray; Luster: Dull to earthy; Structure: Microcrystalline; Cleavage: None/Fragmentary; Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Cream, tan, or light gray
Luster: Dull to earthy

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Cream, tan, or light gray; Luster: Dull to earthy; Structure: Microcrystalline; Cleavage: None/Fragmentary; 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 chemically through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used extensively in construction (as ballast and building stone), cement production, as a soil conditioner in agriculture, and as a component in glass making.

Geological facts

It contains a high percentage of the world’s oil and natural gas reservoirs. Most caves are formed in limestone when acidic groundwater dissolves the rock over millions of years.

Field identification & locations

Identify in the field using a 'fizz test' (dilute hydrochloric acid or vinegar will cause it to bubble). Commonly found in ancient sea beds and mountain ranges that were once underwater.