sedimentary

Limestone (Grey and White specimens)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Grey to creamy white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal to irregular fracture); Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Grey to creamy white
Luster: Dull to earthy

Identified March 4, 2026More sedimentary →

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Physical properties

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 water or during the lithification of lime mud. It spans most geological ages from Precambrian to Cenozoic.

Uses & applications

Used extensively as a building material, aggregate for concrete, manufacture of lime and cement, soil conditioner in agriculture, and as a flux in steel making.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary host rock for many cave systems worldwide because it is easily dissolved by acidic groundwater.

Field identification & locations

Identify in the field by applying a drop of dilute hydrochloric acid (or vinegar), which will cause the specimen to effervesce (fizz). Commonly found in areas that were formerly ancient seabeds; check quarries and road cuts.

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