Mossbauer characterization of iron oxides and (oxy)hydroxides: the presentstate of the art

Mossbauer spectroscopy is a powerful direct technique for the identificatio n and quantification of iron oxides and (oxy)hydroxides in soils and sedime nts. However, further characterization with respect to structural propertie s such as crystallinity, Al substitution, stoichiometry, water content, etc . is rather limited. With some examples of synthetic and natural goethite a nd hematite sample series it is illustrated that the hyperfine parameters d epend on much more structural features than the Al content and crystallinit y alone. Neither the Morin transition in hematite nor the Verwey transition in magnetite is directly applicable for analytical purposes in natural sam ples.