The Garfield and Uley nontronites - an infrared spectroscopic comparison

FTIR and Infrared emission spectroscopy (IES) has been used to characterise the Uley (Australian) and Garfield nontronites. These clay minerals are characterised by a strong emission band at 3570 cm-1 attributed to the FeFeOH unit. Dehydroxylation is followed by the loss of intensity of this band as a function of temperature. Dehydroxylation is also followed by the loss of intensity of the FeFeOH deformation vibration at 843 cm-1. IES shows that the dehydroxylation occurs as a continuous process in comparison to DTA/TGA studies where the dehydroxylation occurs abruptly at 425 degrees Celsius. Water in these high iron bearing smectites have been observed through the stretching mode at 3430 cm-1 and the bending mode at 1630 cm-1. Different types of water are identified in the nontronite structure by the analysis of the band profile in the 1590 to 1680 cm-1 region. Low frequency vibrations show that the Uley green nontronite is similar to the Garfield nontronite. The brown Uley nontronite is closer to the Hohen-Hagen nontronite. The Uley nontronites may therefore be used spectroscopically to replace other nontronites as a reference clay mineral.