Limestone

Carbonate sedimentary rock composed of skeletal or precipitated calcite and aragonite from shallow marine shelves.

Specifications & Metrics

type: Sedimentary Rock
composition: Calcite and aragonite (CaCO₃), with minor dolomite, chert nodules, and clay
texture: Bioclastic (fossiliferous), micritic (carbonate mud), oolitic, or travertine
silica content: <5–10 wt% detrital silicates
density: 1.5–2.7 g/cm³ (porosity-dependent)
tectonic setting: Warm shallow continental shelves, carbonate platforms, reefs, and karst aquifers

Comprising 20% to 25% of all sedimentary rocks, Phanerozoic limestone forms primarily on warm, shallow marine platforms from the accumulated calcium carbonate shells and skeletons of foraminifera, corals, molluscs, coccolithophores, and crinoids.
In Robert Dunham's textural classification, limestones are graded from carbonate-mud-supported mudstone and wackestone to grain-supported packstone, grainstone, and reef-framework boundstone.
Calcining limestone above 825 °C drives off CO₂ to yield quicklime (CaO), the essential chemical feedstock for Portland cement and mortar, while natural limestone formations host roughly 30% of global petroleum reservoirs.