Mossbauer measurements performed between 5 and 300 K on polycrystalline powder of an iron-carbonyl derivative of C-60 reveal two inequivalent iron sites. The first site displays a quadrupole split doubler at all temperatures, assigned to an [{Fe(CO)(4)}(x)(eta(2)-C-60)] adduct (X unknown). This iron site presents an S = 0 spin state and a negative isomer shift indicating that C-60 acts as an electron pair donor to the metal center. The average effective hyperfine field for the second site is characteristic of an Fe(III) high-spin (S = 5/2) state and exhibits relaxation effects, This Fe(III) sextet splits into two subspectra, on the application of a magnetic field, which can be assigned to the octahedral and tetrahedral sites of gamma-Fe2O3 microparticles formed on the grain surface.