The quantitative estimation of fluxing ability (F_A) of silicate-limy ores and copper-smelting production’s slags is developed taking into account their chemical and phase composition, which is offered to estimate as a difference between the total quantity of silica and calcium oxide and their quantity in compounds. Fluxing ability can have positive and negative value depending on the content of basic flux components (SiO₂, CaO) and combination of compounds in a material. The dependence of influence of homogeneous slags fluxing ability on the copper content in them is presented on the basis of experimental and industrial data. Classification of silicate-limy materials fluxing ability is developed on the basis of F_A and decreptation for ores and F_A and meltability for slags.