Ooid-limestone

An even-textured limestone composed almost wholly of relatively uniform calcareous ooliths (ooids), with virtually no interstitial material. It is locally an important oil reservoir (such as the Smackover Formation in Arkansas), and is also quarried for building stone.

Often simply called oolite, though this can include non-carbonate rocks.

The mineralogical nature of the oolites depends, as a rough rule, on the Mg content of the seawater: at high Mg contents (e.g. ice ages), aragonitic ooids are precipitated; at low Mg contents, calcitic ooids are precipitated. Subsequent recrystallisation processes can transform aragonitic ooids into calcitic ones.