sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite crystals; Specific Gravity: 2.5–2.7

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

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Widely used as a building material, in the manufacture of cement, as an aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, and as a soil conditioner.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock found in karst landscapes, which are characterized by caves and sinkholes.

Field identification & locations

Identify in the field by its softness (can be scratched by a penny) and its effervescence (fizzing) when a drop of dilute hydrochloric acid or strong vinegar is applied. Common worldwide in ancient seabed locations.