sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Cream, tan, or light brown; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None visible in hand specimen; Specific gravity: 2.3 to 2.7

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

Identified July 6, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Primarily used in construction as an aggregate for road base and railroad ballast, in the production of cement and lime, and as building stone.

Geological facts

Limestone makes up about 10 percent of the total volume of all sedimentary rocks. It often contains fossils of the organisms that lived in the shallow seas where it formed.

Field identification & locations

Identify in the field by its light color, soft texture (can be scratched by a copper penny), and its tendency to effervesce (fizz) when exposed to a weak acid like vinegar.