Metasomatism is the replacement of a substance by another due to changes in the temperature, pressure and chemical composition of a solution. It is a mass transfer process involving the injection and escape of substances. The metasomatism process takes place in the presence of a solid and a solution, and the dissolution of the original mineral and the formation of new minerals occur simultaneously. The chemical composition of the original rock changes, and the newly formed rocks have various metasomatic structures. These are the two prominent characteristics of metasomatism.