Mössbauer studies of some sulphide minerals

Mössbauer spectra of the mineral sulphides mackinawite (Fe_1+xS), greigite (Fe₃S₄) and pentlandite (Ni, Fe)₉S₈ have been studied at different temperatures and in external magnetic fields. The spectrum of mackinawite obtained at 4·2°K and in an external magnetic field of 30 Kg has confirmed the presence of low-spin ferrous iron. Study of the low temperature spectra of greigite prepared by different methods suggests the presence of differing amounts of high-spin ferrous and ferric iron. Examination of the spectrum of pentlandite at 4·2°K in an external field also shows the presence of low-spin iron and the problem of the valence of iron and ordering of iron atoms between different sites is discussed.