THE INFLUENCE OF IONIC ENVIRONMENT ON THE NATURE OF IRON OXIDES IN SOILS

The colour in a sequence of soils formed on basalt in the Burnie area of Tasmania changes from red to red-brown near sea level to a yellow-brown in the more elevated areas. This colour change reflects the variations in the goethite/haematite ratio which in turn has been positively correlated to the proportions of Ca plus Mg on the exchange complex. The results support the laboratory observations of Schellmann that the adsorption of Ca and Mg ions by freshly precipitated iron oxide gel directs the ageing towards haematite.