What does "concretion" mean?

Concretion: A mass or nodule of solid matter formed by growing together, by congelation, condensation, coagulation, induration, etc.; a clot; a lump; a calculus. Accidental ossifications or deposits of phosphates of lime in certain organs . . . are called osseous concretions. Dunglison.

Additional senses

  1. 2.(Geol.) A rounded mass or nodule produced by an aggregation of the material around a center; as, the calcareous concretions common in beds of clay.

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