Trace element speciation in magnetite and pyrite. Magnetite is one of the most common spinel group mineral described by general formula AB 2 O 4, where A is usually replaced by divalent cations such as Mn 2+, Ni 2+, Mg 2+, Co 2+ or Zn 2+, and B can be substituted by trivalent such as Al 3+, Cr 3+, V 3+ or Ga 3+ (Lindsley, 1976, …