Secondary steelmaking slags contain numerous types of minerals such as larnite and various Ca-aluminates. Fresh ladle slags are unstable in the atmosphere disintegrating into fine white dust. The modification change of larnite (C₂S) is the main cause of this phenomenon. The freshly formed white slag powder is unprotected against wind erosion. When water is sprinkled on it, however, a solid crust is formed instantly. According to the results, this hard layer contains calcium aluminate hydrate causing quick bonding and reducing the threat of wind erosion significantly. The major composing minerals of slags belong to two groups: the gehlenite–akermanite series belonging to sorosilicates and the larnite–bredigite series that belong to nesosilicates. In very small quantities these slags also contain various heavy metals. The most characteristic among them is barium that is mostly precipitated as non-soluble barite in the course of the disintegration of the slag therefore it presence no environmental risk. The chemical composition of slags determines their possible utilization which is also discussed in the paper.