Reflected light microscopy can contribute important information regarding the mineralogy, mineral abundance, internal textures, sizes and shapes of particles in electric arc furnace (EAF) dusts. Scanning electron microscopy-energy dispersive spectroscopy and electron microprobe analysis are useful to determine the chemical compositions of the specific mineral grains in the dust particles. Furthermore, the mineralogical reactions that have taken place during the pyro-metallurgical treatment of EAF dusts and the mineralogy and textural character of those treated dust samples can be directly observed by reflected light microscopy. Such studies are useful in monitoring the efficiency of experimental pyrometallurgical treatment of EAF dusts which are designed to render them nonhazardous.