The resonant ionization of Xe(nf) Rydberg atoms in extreme red and blue Stark states at a conducting surface is investigated. The Xe( nf) Rydberg atoms are created by laser induced photoexcitation of xenon 6s'[1/ 2]0 metastable atoms created within a DC discharge. Following ionization the resulting Rydberg ion core is attracted to the surface by its image charge where it will be neutralized. To prevent this, an electric field is applied perpendicular to the surface. The critical field required to observe the ions provides a measure of the atom/surface separation at which resonant ionization occurred. The data show that the extreme members of a given Stark manifold ionize at similar atom/surface separations pointing to strong perturbations in the energies and structure of the atomic states induced by the presence of the surface.