The MgO concentration in the magnesium-rich palygorskite is 16.23, which is almost twice its concentration in the magnesium-poor palygorskite, whereas the Fe2O3 concentration in magnesium-poor palygorskite is almost twice its concentration in magnesium-rich palygorskite. The thermal behaviors vary with the chemical composition of the palygorskite. The results of phase analysis, which was carried out with the purified samples which had been heated and kept at a certain temperature for 2 h, show that magnesium-poor palygorskite experienced water depletion and glassy phase.