sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: White, cream, or light gray; Luster: Dull to earthy; Texture: Fine-grained to clastic; Cleavage: None (fractures irregularly); Specific Gravity: 2.3-2.7

Hardness: 3 (Mohs scale)
Color: White, cream, or light gray
Luster: Dull to earthy

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: White, cream, or light gray; Luster: Dull to earthy; Texture: Fine-grained to clastic; Cleavage: None (fractures irregularly); Specific Gravity: 2.3-2.7

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 calcium-rich water in caves or springs.

Uses & applications

Extensively used in construction as building stone, road base, and a key ingredient in cement. It is also used as a soil conditioner in agriculture and as a filler in toothpaste and plastics.

Geological facts

Limestone covers about 10% of the Earth's total land surface. Most of the world's spectacular cave systems, like Mammoth Cave, are carved out of limestone by acidic groundwater.

Field identification & locations

Identify in the field using the 'acid test'—it will fizz (effervesce) when a drop of diluted hydrochloric acid or strong vinegar is applied. It is commonly found in areas that were once ancient shallow sea beds.