This paper presents the results of the first experimental thermochemical study of the Al-rich palygorskite (Al2Mg2)[Si8O20](OH)(2)(H2O)(4)center dot 5H(2)O (Crimea, Ukraine) made with the help of a high-temperature heat-flux Tian-Calvet microcalorimeter. The natural palygorskite was characterized by scanning electron microscopy, X-ray fluorescence analysis, X-ray powder diffraction, thermal analysis, FTIR spectroscopy. The standard molar enthalpies of formation from the elements were determined by the melt solution calorimetry for palygorskite with various content of different types of water in accordance with Hess's law. The values of the standard enthalpies of formation at T = 298.15 K were found to be -(12,560 +/- 36) kJ.mol(-1) for (Mg2Al2)[Si8O20](OH)(2)(H2O)(4)center dot 3.5H(2)O; -(11,535 +/- 26) kJ.mol(-1) for (Mg2Al2)[Si8O20](OH)(2)(H2O)(4) and -(10,353 +/- 16) kJ . mol(-1) for (Mg2Al2)[Si8O20](OH)(2). On the basis of experimental data for natural Al-rich palygorskite the thermodynamic properties of Mg-rich palygorskite and palygorskite with intermediate (Al + Mg) composition were calculated. The enthalpies of removal of different types of water were measured. It was found that the value of enthalpy of removal of adsorbed and zeolitic water was significantly lower than the enthalpy of removal of the coordinated water, it corresponds to the greater bond strength of coordinated water than adsorbed and zeolitic water in the structure of layered minerals of (palygorskite + sepiolite) group. (C) 2015 Elsevier Ltd. All rights reserved.