sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: earthy or dull; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.7.

Hardness: 3 on Mohs scale
Color: typically white, gray, or tan
Luster: earthy or dull

Identified June 29, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: earthy or dull; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 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

Extensively used as a building material, aggregate for concrete, road base, raw material for cement, and in the production of lime. Also used as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the Great Pyramids of Giza were originally covered in white tura limestone casings.

Field identification & locations

Identified in the field by its softness (can be scratched by a penny) and its strong effervescence (bubbling) when it comes into contact with dilute hydrochloric acid.