Abstract Physical and chemical features of natural clays have been studied using the methods of X-ray diffraction, chemical, thermal and spectral analyses, ESR and IR spectroscopy; the nature of their medical properties being considered. The composition of macro and trace impurities in the clays has been analysed. The medical properties of the clays are determined by the presence of almost all the chemical elements necessary for normal functioning of a living organism as well as by sorption features due to a specific character of crystal structure. Using ESR technique, the forms of occurrence for some trace impurities (Mn 2+ , Fe 3+ ) and for paramagnetic centers (PC) of the radiation nature have been determined. The intensity of PC response has been shown to correlate with the content of actinoid ions such as U and Th in the samples. Basing on the ESR spectral data it has been established that blue color of the clays is caused by V 4+ impurity ions V 4+ in the form of vanadyl VO 2+ . The content of the microelements such as vanadium, boron and chromium in blue kaoline ãëèíàõ has been demonstrated to be 10-15 times higher as compared to clay samples of another coloring. An important role of complex influence of macro-and microelements (silicon-boron, vanadium-chromium, manganese, etc.) on the enzymes and hormones in various organs, as well as the presence of such combinations of chemical elements in blue clays have been noted
