Abstract MnS clusters were prepared by treating laumontite zeolite with 0.1 N aqueous manganese nitrate solutions at 296 K (pH 5.8), using a solid/liquid ratio of 1/50, followed by a sulfidation process with H2S, at 350 K, during 12 h. XRD and magnetic resonance measurements proved that the clusters are formed inside the zeolite channels. Examination of SEM revealed that no disintegration of zeolite framework had occurred during the synthesis. The 27Al MAS NMR spectra of the zeolite framework showed three main resonances in the 30–60 ppm region, which are attributed to distinct Al species. The NMR spectra indicate that structural changes occurred in the tetrahedral framework during the sulfidation process. EPR measurements performed at room temperature evidenced three different Mn species, which are affected by the sulfidation process. The local field effect is shown to be substantial for semiconductor clusters encapsulated in laumontite.