Summary Evolution of the external surface area and the two types of microporosity of attapulgite (structural and inter-fiber) were examined as a function of a vacuum thermal treatment upt to 500°C. The methods used include: controlled transformation rate thermal analysis, N2 and Ar low temperature adsorption calorimetry, water vapor adsorption gravimetry and quasi equilibrium gas adsorption procedure of N2 at 77K and CO2 at 273 and 293K. Depending on the outgassing conditions, i.e. the residual pressure, the structure folds 150 to 70°C. For lower temperature, only a part (18%) of the structural microporosity is available to N2, 13% to argon and 100% to CO2. With water, the structure can rehydrate after the structure is folded up to an outgassing temperature of 225°C.