Thermal behaviour of natural vermiculite (Santa Olalla, Huelva, Spain) was investigated by TG, DTA, emanation thermal analysis
(ETA) and high temperature XRD on heating in the temperature range from 30 to 1100°C before and after vibratory mill grinding.
Microstructure changes of natural and ground vermiculite samples were characterized by using ETA under in situ conditions
of heating. By comparing the ETA and XRD results it was demonstrated that a decrease of radon release rate measured by ETA
characterized the decrease in the interlayer spacing of the vermiculite samples that followed the dehydration.