The mineralogy, texture and composition of rocks associated with the kaolin deposits in the Ahirozu-Hamidiye-Ucbasli area, SE of Mihaliccik, Eskisehir, Turkey, were investigated. In the study area, Triassic, blue-green schists and serpentinized ultramafic rocks are exposed. Kaolinization occurs at the contact between a Triassic granitic intrusion and metamorphic rocks. Textural and mineralogical characteristics were identified by X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analyses. The effects of hydrothermal alteration on the whole-rock chemical composition were determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. Homogenization temperature (T-h, degrees C), salinity, (wt.% NaCl) and melting temperature (T-m, degrees C) were detected by fluid-inclusion analyses.