Ooids usually form on the sea floor, most commonly in shallow tropical seas (around the Bahamas, for example, or in the Persian Gulf). After being buried under additional sediment, these ooid grains can be cemented together to form a sedimentary rock called an oolite.

Where are Oolites deposited?

Oolitic limestone is made up of small spheres called ooiliths that are stuck together by lime mud. They form when calcium carbonate is deposited on the surface of sand grains rolled (by waves) around on a shallow sea floor.

Where are ooids forming today?

Today ooids are to be found in a number of locations with warm shallow water, including the Bahamas, Shark Bay in Australia, and the Persian Gulf, all of which are marine sites; but they are also sometimes found in inland waters such as the Great Salt Lake in Utah.