sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3-4 (Mohs scale); Color: White to light grey; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.3-2.7

Hardness: 3-4 (Mohs scale)
Color: White to light grey
Luster: Dull to earthy

Identified May 3, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: White to light grey; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.3-2.7

Formation & geological history

Formed primarily in marine environments through the accumulation of shell, coral, algal, and fecal debris, or through chemical precipitation. Occurs throughout all geological ages.

Uses & applications

Extensively used as a building material, in the manufacture of lime and cement, as an aggregate in road construction, and as a flux in steel production.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary material found in caves, where it is dissolved by acidic water to form stalactites and stalagmites.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its effervescent reaction to dilute hydrochloric acid. Commonly found in coastal areas and ancient seabed deposits.