This study presents the preparation, characterization and activity of a novel natural mineral-based catalyst for the ozonation of water recalcitrant compounds. The raw and calcined magnetite had the specific surface area of 27 m(2)/g and 34 m(2)/g, respectively. The effects of solution pH, catalyst dose, model dye concentration, and reaction time on the degradation and mineralization of a selected reactive azo dye viz. Reactive Red-120 (RR-120) were evaluated. Calcined magnetite attained greater catalytic potential than the raw ore in the degradation of RR-120. Oxidation via radical species on the surface of the catalyst was the main mechanism of RR-120 degradation in the developed catalytic ozonation process, occurring with a pseudo-first-order reaction rate at a constant of 0.082 min(-1) under the optimum pH of 11 and catalyst dose of 3 g/L. Accordingly, considering its abundance in nature together with its very high catalytic potential, calcined magnetite is a promising and reliable catalytic material for the ozonation of inhibitory and recalcitrant compounds in water and wastewater. (C) 2012 Elsevier B.V. All rights reserved.