The Gümüşköy kaolin clay deposit, located ~40 km northwest of Kütahya, Turkey, has promising reserves for ceramic production. In order to evaluate the potential use of this region, five representative clay samples were collected and characterized with X-ray diffraction, polarized light optical microscopy, X-ray fluorescence spectrometry, differential thermal analysis and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. According to the Chemical Index of Alteration and Plagioclase Index of Alteration, the kaolin samples were formed by strong chemical alteration of the Tavşanlı volcanites. The clays contain kaolinite, illite, pyrophyllite, montmorillonite and minor halloysite, as well as quartz, plagioclase (andesine), biotite, sanidine, rutile and goethite. The clay samples were used for thermal and physical tests. The plasticity, particle-size distributions firing properties (water absorption, apparent porosity, linear shrinkage, dry bending strength, fired bending strength) and colour parameters of the fired samples were determined. The kaolinitic clay samples from Gümüşköy are suitable for making wall tiles, floor tiles and kiln wares after shaping by dry pressing and extrusion.