sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Off-white, grey, tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.5-2.7

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

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Off-white, grey, tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.5-2.7

Formation & geological history

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

Uses & applications

Used extensively in construction (aggregate, cement), agriculture (soil conditioner), and as a base material for roads. Also used for lime production and in architecture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary material found in karst landscapes, where it dissolves to form caves and sinkholes.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbles) when a drop of dilute hydrochloric acid or vinegar is applied. Found globally in ancient seabed deposits.