sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray, tan, or beige; Luster: Dull to earthy; Structure: Often contains visible fossil fragments or tiny shells; Cleavage: None; Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Gray, tan, or beige
Luster: Dull to earthy

Identified May 23, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray, tan, or beige; Luster: Dull to earthy; Structure: Often contains visible fossil fragments or tiny shells; Cleavage: None; 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 via precipitation from calcium-rich water in caves or springs.

Uses & applications

Extensively used in construction as an aggregate, in the manufacture of cement, and as a soil conditioner in agriculture. Pure forms are used in the chemical and glass industries.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It is the primary material found in many famous caves and karst landscapes.

Field identification & locations

Identify in the field by its light color and the 'fizz' test: it will bubble when a drop of diluted hydrochloric acid or white vinegar is applied. Commonly found in areas that were once prehistoric seafloors.