sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale. Color ranges from white, gray, yellow to brown. Luster: earthy to subvitreous. Crystal structure: trigonal (when in calcite form). Cleavage: perfect in three directions (rhombohedral). Specific gravity: 2.7 - 2.9.

Hardness: 3 on the Mohs scale
Luster: earthy to subvitreous

Identified July 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed mainly through the accumulation of skeletal fragments of marine organisms like coral, algal, and foraminifera, as well as chemical precipitation of calcium carbonate from water. It forms in shallow, warm marine waters and dates from various geological ages, ranging from the Precambrian to recent.

Uses & applications

Widely used in construction as a building material, as aggregate for road bases, as a main ingredient in the manufacture of Portland cement, in agriculture to neutralize acidic soil, and in the production of lime.

Geological facts

Limestone often contains fossils of ancient marine life. Famous structures built from limestone include the Great Pyramid of Giza and the Parthenon in Athens.

Field identification & locations

Easily identified in the field by its characteristic fizz or effervescence when a drop of weak hydrochloric acid (or vinegar) is applied, due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.