sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: typically grey, white, or tan; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.5–2.7

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

Identified June 20, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: typically grey, white, or tan; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.5–2.7

Formation & geological history

Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used extensively in construction (as building blocks and aggregate), in the manufacturing of cement, as a soil conditioner in agriculture, and in the production of lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most caves are formed in limestone when acidic water dissolves the rock over millions of years.

Field identification & locations

Identification includes a fizz test (reaction to dilute hydrochloric acid). Look for fossil remains or a fine-grained, earthy texture. Common in areas with ancient seabeds.