The process of grinding of coarse particles of glass-like slag from the ferro-nickel industry in a high-speed ball mill has been studied. The disintegration of slag particles first occurs at the places of ferrous oxide accumulations. Then, the glass-like component of slag particles (calcium silicate) is destroyed accompanied with the formation of the surface defect layer that is easily transformed into calcium hydrosilicate. Further grinding results in the consolidation of slag particles around the ferrous oxide accumulations and in the formation of dense aggregates. The surface defect layer of the glass-like calcium hydrosilicate particles changes into calcium hydrosilicate more efficiently when dispersed in water. This promotes the development of binding properties.