Fe2IIIS3-II + 3 O20 2 Fe0 + 3 SIVO2-II

This is an oxidation-reduction (redox) reaction:

3 S-II - 18 e- 3 SIV (oxidation)

2 FeIII + 6 e- 2 Fe0 (reduction)

6 O0 + 12 e- 6 O-II (reduction)

Change the oxidation states