sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs); Color: White to light grey; Luster: Dull to earthy; Structure: Fine-grained clastic or crystalline; Specific Gravity: 2.3-2.7.

Hardness: 3 (Mohs)
Color: White to light grey
Luster: Dull to earthy

Identified July 13, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs); Color: White to light grey; Luster: Dull to earthy; Structure: Fine-grained clastic or crystalline; Specific Gravity: 2.3-2.7.

Formation & geological history

Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. Can also form through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Widely used as an architectural stone, in the production of cement, as an aggregate for the base of roads, and as a white pigment or filler in products like toothpaste or paints.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the world's caves are formed in limestone because it is soluble in slightly acidic water.

Field identification & locations

Identified in the field by its softness (can be scratched by a penny) and by effervescing (fizzing) when in contact with a weak acid like vinegar. Found in massive layers in mountain ranges and plateaus.