sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Cream, tan, or light grey; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/clastic; Specific gravity: 2.5-2.7

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

Identified June 2, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Cream, tan, or light grey; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/clastic; 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

Extensively used in construction as an aggregate, in the manufacture of lime and cement, as a decorative building stone, and in agricultural soil treatment.

Geological facts

Limestone can contain fossils of ancient marine life. It is the primary component of many cave systems because it is soluble in weak acidic solutions like rainwater.

Field identification & locations

Identify in the field by its light color and the 'fizz' test (it reacts and bubbles when exposed to diluted hydrochloric acid). Commonly found in areas that were once prehistoric ocean floors.