Traditional rock wool fibres are susceptible to crystallization and pulverization. To mitigate this, glass fibres were produced from iron ore waste (IOW). When the ratio of Fe²⁺ and Fe³⁺ is 1:3 and the Al₂O₃ content is 10 wt.%, increasing the Fe_xO_y content enhances the thermal stability.At an Fe_xO_y content of 17–19% and an Al₂O₃ content of 10–13%, the glass transition temperature (Tg) peaked. Increasing the Fe_xO_y content from 10% to 20% enhanced the stability of Si-O and Al-O bonds and increased bridged oxygen, stabilizing the structure. Here, Fe²⁺ balances structural charges, while Fe³⁺ replaces some Al atoms in the network. When the Al₂O₃ content is 10–13% and the Fe_xO_y content is 17–19%, the thermal stability of the IOW rock glass reaches its optimal level. At 20% Fe_xO_y content, the structure becomes three-dimensional and cyclic, increasing polymerization. Consequently, incorporating Fe_xO_y alongside a 10% Al₂O₃ content improves thermal stability, supporting the development of high-stability rock wool from IOW. This approach also enhances the refractory properties of rock wool fibres within the Fe_xO_y-Al₂O₃-SiO₂-MgO-CaO system.