Oolith (out griech. oon, egg and lithos, stone; also pea stone or Rogenstein mentioned) is a sedimentary rock, which consists of small mineral balls (Ooiden), which are cemented by a kalkiges or toniges bonding agent. The Ooide predominantly consists of lime (Calcit or aragonite) or also of iron hydroxide or silicic acid. They have usually a diameter from 0,5 to 2 millimeters.
Ooide develop in warm lime-surfeited water with strong undulation. Starting point are small particles such as z. B. Sandkörner or fragments of shell bowls, which are held by the undulation in the Schwebe and seeds to form, at which lime settles in concentric bowls or in the form of radialfibrous Kalzitkristallen. If this Ooide became too heavy, then they drop to the sea-bottom and form a sediment layer, in which they are rolled by water movement. Oolith results from the solidification of this sediment layer to rock (dia. genesis).
Oolith is named-giving for the Gesteinsformation of the Korallenoolith, forwards approx. 155 to 150 millions Years one deposited in upper law (Malm). In the Korallenoolith both Kalkoolithe and oolithische iron ores are to be found.