A SWELLING DIOCTAHEDRAL CLAY MINERAL OF A VERMICULITE-SMECTITE TYPE IN THE WEATHERING HORIZONS OF PODZOLS

In Scandinavian podzols a swelling dioctahedral mineral, probably de-rived from dioctahedral mica and iron-rich chlorite, has been found in the clay (<2/~) fractions from As-horizons. This mineral, or group of minerals, is shown by X-ray examination and differential thermal analysis to be of a vermiculite-smectite ype, thus making the differenti-ation between vermiculite and smectite still more problematical. The pretreatment of the samples and choice of interlayer cations is shown to be of great significance for the identification of soil clay minerals