Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

The Gibbs free energy formation ( Δ_fG) of Cu₂S is less than that of H₂S and CS₂. Therefore, H₂ and C cannot reduce Cu₂S to Cu.

On the other hand, the Gibbs free energy formation of Cu₂O is greater than that of CO. hence, C can reduce Cu₂O to Cu.

C (s) + Cu₂O (s) → 2Cu (s) + CO (g)

Hence, the extraction of copper from its pyrite ore is difficult than from its oxide ore through reduction.