con·cre·tion 
(kən-krēshən)
(kən-krēshən)n.
1.
a. The act or process of concreting into a mass; coalescence.
b. The state of having been concreted: a concretion of seminal ideas in her treatise.
2. A solid hard mass.
3. Geology A rounded mass of mineral matter found in sedimentary rock.
4. Medicine A solid mass, usually composed of inorganic material, formed in a cavity or tissue of the body; a calculus.
con·cretion·ar′y (-shə-nĕr′ē) adj.