Ooid

Ooids (Gr. oon "egg" ) are spherical - oval, pea-sized mineral body, which form from concentric or radial- fibrous Anwachsschalen a mostly different type of core. Ooids may consist of different minerals, most commonly Kalkooide. Like particles with a larger diameter are the Pisoide.

Oolites are sedimentary rocks and consist of ooids, which are cemented with a binder. They are depending on the mineral named differently ( Rogenstein, pea stone, Eisenoolith, Kieseloolith ).

Education

Prevent the formation of ooids, two conditions are necessary. Firstly, a high concentration of calcium carbonate in the water must be present ( supersaturated solution ), and the water kept moving to the other in order for the forming ooids retain their round shape. Therefore, lagoons, where prevail slight undulations, education rooms for ooids.

If the two conditions described previously met, is a crystallization nucleus, for example, a grain of sand, a prerequisite for the formation of ooids. To this germ is now layers of lime or iron begin to separate from the water. This process continues until the body is too heavy and sink to the bottom. Therefore Ooide also have nearly the same size. In some ooids, the nuclei still show.

Eisenooide

Eisenooide are ooids from limonite ( limonite ) or hematite ( hematite ). These are formed in the sea and represent Eisenhydroxidfällungen, which attach themselves to kaolinite.