sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Tan, beige, or gray; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, though often inconspicuous in rock form.

Hardness: 3 on Mohs scale
Color: Tan, beige, or gray
Luster: Dull/Earthy

Identified May 17, 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 waters.

Uses & applications

Used extensively in construction as road base, concrete aggregate, and building stone. Also used in the production of lime, cement, and as a soil conditioner in agriculture.

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 easily dissolved by slightly acidic groundwater.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbling) when in contact with dilute hydrochloric acid or strong vinegar. Common in karst landscapes and coastal cliffs.