sedimentary

Limestone

Calcite-rich Sedimentary Rock (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white, off-white, or light gray; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite microcrystals); Cleavage: Perfect rhombohedral (not always visible in rough form); Specific Gravity: 2.7

Hardness: 3 on Mohs scale
Color: typically white, off-white, or light gray
Luster: dull to earthy

Identified March 22, 2026More sedimentary →

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Physical properties

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. Age varies widely from Precambrian to Holocene.

Uses & applications

Extensively used in construction (cements and road base), agriculture (soil conditioner), industrial chemical production, and as an ornamental architectural stone.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. Most of the world’s caves are formed in limestone because it is easily dissolved by slightly acidic groundwater.

Field identification & locations

Can be identified in the field by its softness (can be scratched by a copper penny) and its strong effervescence (fizzing) when reacting with dilute hydrochloric acid. Commonly found in former ocean basins and quarries worldwide.

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