sedimentary

Limestone

Calcium carbonate rock (predominantly Calcite, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Off-white, cream, light grey to beige; Luster: Dull, earthy; Texture: Fine-grained to microcrystalline; Cleavage: None visible in massive rock, calcite component shows rhombohedral cleavage; Specific Gravity: ~2.5-2.7

Hardness: 3 on Mohs scale
Color: Off-white, cream, light grey to beige
Luster: Dull, earthy

Identified October 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily by the accumulation and compaction of organic debris (such as shells, coral, algal, and fecal debris) or precipitation of calcium carbonate from shallow, warm marine waters over millions of years.

Uses & applications

Extensively used in construction as crushed stone, aggregate, building stone, and dimension stone; essential ingredient in the manufacture of Portland cement and lime; soil conditioner in agriculture; flux in smelting.

Geological facts

Limestone comprises roughly 10% of the total volume of all sedimentary rocks on Earth. Landscapes dominated by limestone dissolution often develop dramatic karst topography, featuring sinkholes, underground caves, and stalactites.

Field identification & locations

Field identification is easily confirmed by vigorous effervescence (bubbling) when exposed to cold, dilute hydrochloric acid (acid test), alongside its relatively low hardness (can be easily scratched with a copper coin or pocket knife). Abundantly found globally in marine sedimentary basins.