Concretion

Concretion is a term used in the fields of biology and mineralogy.

Biology

A concretion is a solid foreign body that forms in tissue or in an organ, such as gallstones or kidney stones, and sodium urate tophus.

Mineralogy

Mineral mass formed by precipitation around a fragment of material. If this material occurs in a pure state, the concretion is white or transparent if its size is small. Impurities contained in the rock, especially iron oxide, are responsible for the ochre colour of concretions.