In , the Raman spectra of FeO, Fe3O4, α-Fe2O3, α-FeOOH, and γ-FeOOH, which are "the common products of iron oxidation", are given. "Raman spectra of the oxides of iron can be obtained with little difficulty using conventional instrumentation. … Spectra of thin surface films are identical to those of the pure compounds comprising the films" . Thibeau and coworkers add that it is observed "considerable variation in intensity of Raman scattering from these oxides. The black compounds, FeO and Fe3O4, give weak spectra, whereas those which are lighter in color, α-Fe2O3, α-FeOOH, and γ-FeOOH, give stronger spectra".