A sedimentary rock that is composed largely of carbonate minerals, especially carbonates of calcium and magnesium. Calcite and aragonite are the chief minerals; dolomite is also present in the dolomitic limestones. There are many varieties of limestones but most are deposited in shallow water. Organic limestones (e.g. chalk) are formed from the calcareous skeletons of organisms; precipitated limestones include oolite, which is composed of ooliths—spherical bodies formed by the precipitation of carbonate around a nucleus; and clastic limestones are derived from fragments of pre-existing calcareous rocks.
Geology and Earth Sciences
Sedimentary type of rock composed mainly of calcite and/or dolomite, which is often of organic, chemical, or detrital origin. Seefolk limestone classification; dunham classification; leighton–pendexter classification.