sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: light gray, tan, or white; Luster: earthy to dull; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.3–2.7

Hardness: 3 (Mohs scale)
Color: light gray, tan, or white
Luster: earthy to dull

Identified April 14, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: light gray, tan, or white; Luster: earthy to dull; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.3–2.7

Formation & geological history

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

Uses & applications

Used widely in construction (aggregate, cement), agriculture (neutralizing soil acidity), and as a precursor for chemical industries. Fine varieties are used in sculpture.

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 groundwater.

Field identification & locations

Identify in the field by its light color and characteristic effervescence (bubbling) when a drop of weak hydrochloric acid or vinegar is applied. Commonly found in former marine basins.