Cu₂S and FeS are present in copper matte. When a hot blast of air passes through a molten matte in a silica coated converter, the matte’s FeS oxidises to FeO. FeSiO₃  (slag) is formed when FeO interacts with SiO₂  (silica) .

2FeS + 3O₂ ⇒ 2FeO + 2SO₂
FeO + SiO₂ ⇒ FeSiO₃

Cu₂S is oxidised to Cu₂O , which then reacts with Cu₂S to produce copper metal when all of the iron has been removed as slag.

2Cu₂S + 3O₂ ⇒ 2CuO₂ + 2SO₂
2Cu₂O + Cu₂S ⇒ 6Cu + SO₂