Steelmaking slag and residues from granite cuttings are industrial wastes with considerable production, however limited applications. This work studied an inertization and recovery process of such wastes as raw materials into production of rock wool (i.e. a thermo-acoustic insulator with growing market). Several batches were produced aiming the chemical proprieties of a currently marketed rock wool. Mixtures were casted at temperatures of 1400-1500 °C, then quenched in water and also poured into a Herty Viscosimeter. Produced materials with thickness smaller than 500µm were characterized by chemical analyses, XRD, SEM, EDS and DTA. ThermoCalc software was used to simulate the cooling curves of rock wools. Results showed that incorporation of wastes does not affect the main qualities of rock wool, the thermal insulation and prevention of fire spread. Raw material batches of rock wools may assimilate up to 66% of granite waste, or 53% steelmaking slag, or 70% combining both materials.