Limestone is a sedimentary rock composed mainly of calcium
carbonate (CaCO3), usually calcite, sometimes aragonite. Limestone
may contain considerable amounts of magnesium carbonate (dolomite).
Most limestones have a granular texture, but limestone can also be
massive, crystalline or clastic.
Most limestones are formed by the deposition and consolidation of
the skeletons of marine invertebrates.
Ooid limestone (oolite) is composed mainly from ooids, small (below
2 mm in diameter), spheroidal, coated-layered grains (mostly
consisting of calcium carbonate) that are usually formed on
sea-floors of shallow, tropical seas. Ooids are often aragonitic,
but may also be calcitic or bimineralic (layered,
Calcite-Aragonite).
|