Abstract: More than half of the total borate reserves known in Turkey are concentrated in Kırka (Eskişehir) Region. Clay fractions of marl samples taken from this deposit are investigated by using X-Ray Diffraction, Differential Thermal Analysis chemical techniques.

According to preliminary results of our investigations the clay mineral found in Kırka is a Mg-Montmorillonite. It may be Hectorite, Saponite, Stevensite- Gassulite. Although the presence of Li has been detected in tehese samples the similarity of DTA curves to those of the original Californian Hectorite indicates the presence of mineral Hectorite, final decision can be feached after completion of more detailed studies.