Selected applications of 57Fe Mössbauer spectroscopy to mineral studies

The microscopic models which are commonly used to interpret the temperature variations of the centre shifts and quadrupole splittings observed from the Mössbauer spectra of iron-containing minerals are briefly presented and illustrated using the results of recent studies of ortho- and clinopyroxenes. The importance of applied-field Mössbauer spectroscopy for the determination of the electric field gradient is indicated. Aspects of the magnetic spectra of Fe2+-bearing minerals emphasise the benefit of using external fields to elucidate the nature of the magnetic ordering. Two Fe3+ minerals, bernalite and franklinite, serve as examples to illustrate this point. Finally, two applications of the Mössbauer milliprobe technique are presented: the characterisation of inclusions in diamond, and the determination of the oxidation state of a new iron uranyl sulfate mineral, deliensite.