Concretion

A concretion is an irregular, often roundish designed mineral aggregate, which in a different kind of fine-grained sediment from an aqueous solution circulating (pore water) is ausgesintert.

The concretion is seated at a crystallization center on, mostly due to a different chemical composition, and gradually grows outward on. Examples include Cretaceous flint nodules in chalk, geodes in tone and Lößkindel. The latter, carbonate concretions up to ball size, are also described in soil science. These are generally irregularly - round, up to size of walnuts enrichments of iron and manganese oxides, which form the presence of air in the aerobic phase, in gley and Pseudogleyböden. They are dark brown to black and dissolve mostly on again when the anaerobic phase occurs again. But it can also result in the formation of bog iron.

In the formation of cracks and the subsequent filling of the cracks with the newly formed minerals occur septaria.

Examples

• Moeraki Boulders, New Zealand
• Moqui Marbles, Utah