sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Crystal structure: hexagonal-rhombohedral (as calcite); Cleavage: perfect rhombohedral in crystal form; Specific gravity: 2.71

Hardness: 3 on Mohs scale
Color: typically white, gray, or tan
Luster: dull to earthy

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from ocean water or groundwater (travertine).

Uses & applications

Extensively used in construction as aggregate, road base, and as a component of cement. Also used as a soil conditioner (agricultural lime) and in the production of steel and glass.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary host rock for most of the world's cave systems due to its solubility in slightly acidic water.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper penny) and its effervescence (fizzing) when a drop of dilute hydrochloric acid or strong vinegar is applied. Commonly found in areas with past or present marine basins.