3 Cu2IS-II + 16 HNVO3 6 CuII(NVO3)2 + 3 S0 + 4 NIIO + 8 H2O

This is an oxidation-reduction (redox) reaction:

6 CuI - 6 e- 6 CuII (oxidation)

3 S-II - 6 e- 3 S0 (oxidation)

4 NV + 12 e- 4 NII (reduction)

Cu2S is a reducing agent, Cu2S is a reducing agent, HNO3 is an oxidizing agent.