sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale. Color: Usually white, gray, yellow, or brown. Luster: Earthy to dull. Crystal structure: Trigonal (as calcite). Cleavage: Perfect in three directions (rhombohedral). Specific gravity: 2.7 - 2.9.

Hardness: 3 on the Mohs scale
Color: Usually white, gray, yellow, or brown
Luster: Earthy to dull

Identified July 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in marine environments. Geological age varies widely from Precambrian to Recent.

Uses & applications

Extensively used in construction (as aggregate in concrete and road base), the production of cement, agriculture (soil conditioning), and in the manufacture of glass and paper.

Geological facts

Limestone often contains well-preserved fossils of ancient marine organisms, providing a direct window into Earth's paleontological history. Famous geological features like the White Cliffs of Dover are made almost entirely of chalk, a soft variety of limestone.

Field identification & locations

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