Powder iron monosilicide with certain structure exhibits magnetic properties and can be used as an alloying additive in the production of electrical steels and silicon alloys with special physical and chemical properties. From this point of view, development of the energy-saving technology for receiving such a valuable alloying agent with the disposal of secondary waste is an urgent task. For this purpose, the method of joint aluminothermic reduction of preliminary mechanically activated metallurgical waste is offered. Recently, a method for combining the self-propagating high-temperature synthesis and preliminary mechanical activation for obtaining metal powders with certain phase composition and structure is considered as one of the efficient ones. As the initial materials for obtaining iron monosilicide, the waste (or converter) slags of the Alaverdi copper-smelting plant and molybdenum slags of the Yerevan Pure Iron Plant are used. Besides the mentioned slags, NaNO3 and CaO are added. Properties and structure of the received silicide depend on the contents, quantity of components, and the mass relation of two wastes in the burden. Therefore, the processes of structure formation of the iron monosilicide received from metallurgical waste are investigated. Studies have shown that the best results are obtained in case of waste and molybdenum slag relation of 4:1, when the 60-minute grinding in the vibromill leads to a significant increase in the mechanical activation of the burden. At this relation of FeO and SiO2, a condition is created for receiving iron monosilicide showing magnetic properties. On the whole, those transformations lead to a decrease in the reaction activation power of the interacting substances, an increase of the reactivity capacities, as well as to a new original course of reactions and new modified materials.