A pseudomorph is an alteration product of a crystal that preserves the external euhedral crystal form of the precursor mineral. The pseudomorph may have a different chemical composition and/or crystal structure than the precursor crystal. The pseudomorph can result from replacement of the original structural bonds by formation of new bonds that minimize the energy toward equilibrium in response to changes in the chemical (T, P, X) environment.
Cf., alteromorph, centripetal replacement