sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: White to off-white/gray; Luster: Dull to earthy; Texture: Fine-grained to clastic; Effervesces (fizzles) with dilute acid.

Hardness: 3 on Mohs scale
Color: White to off-white/gray
Luster: Dull to earthy

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: White to off-white/gray; Luster: Dull to earthy; Texture: Fine-grained to clastic; Effervesces (fizzles) with dilute acid.

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Over millions of years, these sediments are lithified into rock through pressure and chemical precipitation.

Uses & applications

Crucial in construction as a building material, aggregate for concrete, and the manufacture of cement. Used in agriculture for neutralising soil acidity and in the steel industry as a flux.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It is the primary material found in caves, where it is often carved into stalactites and stalagmites by water.

Field identification & locations

Identify in the field by its softness (can be scratched by a steel nail) and its reaction to vinegar or HCl. It is ubiquitous in sedimentary basins and often contains visible fossils.