Pyrometallurgical copper extraction generates between 2.2 and 3.0 tons of slag per ton of copper. Copper smelting slag usually contains between 1 and 2 wt pct Cu, resulting in a substantial amount. Effective slag cleaning is critical to enhance copper recovery, often achieved through settling where entrained droplets separate from the slag. Controlling slag viscosity is vital, directly influencing the settling rate and overall efficiency. The literature has limited data on the correlation between viscosity, ionic structure, and the molar ratio of (Al2O3 + SiO2)/MO (MO represents basic oxides) of iron silicate melts. This study investigates how FeO/SiO2 ratio (1.08 and 1.25 at pct/at pct), CaO content (1.2 and 12 at pct), and Al2O3 content (1.4 or 5 at pct) affect the viscosity and melt structure in a FeO–SiO2–Al2O3–CaO–MgO–Cr2O3 system. The study was done by synthesizing the melts, followed by water granulation. The ionic structure was analyzed using Raman spectroscopy, and the viscosity was measured using a high-temperature rheometer. The findings reveal a correlation between melt structure and viscosity, where the viscosity increased when the slag was more polymerized, having a higher content of SiO2 and Al2O3. The study offers insights for optimizing slag properties in industrial settings.