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Talc, Mg3Si40io (OH) 2 is a trioctahedral phyllosilicate with no layer charge. It is macroscopically hydrophobic as it floats naturally. However, water immersion calorimetry measurements reveal that, once outgassed at medium temperatures (100—400 C), it exhibits a strong affinity towards water molecules. Controlled rate thermal analysis measurements coupled with mass spectrometric analyses show that, upon outgassing, different surface species (water, nitrogen, carbon dioxide, and organic molecules) are released from the talc surface. The behavior of the talc surface toward nitrogen, argon, and water as a function of the outgassingtemperature was then studied in detail. The surface presents highly energetic sites for nitrogen and water molecules. These sites are assigned to the hydroxyl groups pointing toward the basal surface of talc through the hexagonal cavity formed by the silica tetrahedra. The adsorption …