In this research, two sepiolite samples of different origins were studied by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, and thermogravimetry. It was observed that both sepiolite samples are nearly pure and well crystallized sepiolite. Thermal studies (thermogravimetry) showed that four distinct weight loss regions are observed in both sepiolite samples studied. It was noticed that these structural changes play an important role to the properties and uses of the sepiolite samples studied. Kinetic parameters of the sepiolite samples were determined by the Arrhenius method at three different heating rates and it was observed that activation energies of the raw and treated sepiolite samples were in the range of 112208 kJ mol-1.