Metastable wurtzite-type (gamma) manganese sulfide (MnS) crystallites were obtained by the reaction between manganese acetate and thioacetamide under the microwave irradiation in dilute aqueous ammonia within 20 min. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). It shows that the reaction time and the additive tri-ethanolamine (TEA) play the important role in eliminating MnOx impurities and favoring the formation of gamma-MnS. (c) 2004 Elsevier B.V. All rights reserved.