In the present paper, two clays from the clay pit in Cobadin-Constantza county are complexly examined. With this aim in view, the following methods are utilised: classical chemical analysis, grain size distribution (sieving and sedimentation with hydrometer), characterisation of clay pastes, X-ray diffraction. Their behaviour of thermal treatment was evaluated by thermal extension, DTA&TG, semi-vitrification characteristics and too X-ray diffraction. The experimental data recommend the use of such clays for building ceramic products.