A small sphere of calcium carbonate no more than a few millimeters in diameter and with a concentric internal structure . These spheres are thought to have formed by inorganic precipitation of calcium carbonate in very thin layers around a grain of sand or a particle of shell or coral. A rock composed primarily of oolites.

A limestone consisting largely of spherical grains of calcium carbonate in concentric spherical layers.

A variety of limestone consisting of round grains like the roe of a fish.

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