We present an investigation of the formation, ionization and fragmentation processes of a new class of clusters consisting of an ionically bound cluster core, coated by a shell of Van der Waals bound atoms. Element specific soft X-ray photoionization spectroscopy was used to investigate the alkali halide cluster core and the Ar coating separately. The thickness of the coating controls the mechanism of ionization and fragmentation of these inhomogeneous clusters. Unusual metastable structures of alkali halide clusters were observed when the thickness of the coating exceeded two monolayers.