CHEMICAL AND RADIOLOGICAL CHARACTERIZATION OF CLAY MINERAL OF PHARMACEUTICAL AND COSMETIC USE P.S.C. Silva, 1 J. G. Cotomácio, 1 L. Farias, 1 D.I.T. Fávaro, 2 B.P. Mazzilli 1 1 Centro de Metrologia das Radiações 2 Centro do Reator de Pesquisas Instituto de Pesquisas Energéticas e Nucleares Av. Prof. Lineu Prestes 2242, Cidade Universitária, CEP 05508 000, São Paulo, Brazil pscsilva@ipen.br Abstract. Since the early days, clays have been used for therapeutic purposes. Nowadays, clay minerals are used as active ingredient or as excipient in formulations for a variety of purposes such as anti-inflammatory, pharmaceutics and cosmetic. Although the large use, few information is available in literature on their content of metals, trace elements and radionuclides. This paper aims to determine the elements (As, Ba, Br, Cs, Co, Cr, Cu, Eu, Fe, Hf, Hg, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Yb, Zn, Zr) and the radionuclides ( 238 U, 232 Th, 226 Ra, 228 Ra, 210 Pb and 40 K) and to discuss the physical-chemical characteristics of Brazilian clays. Keywords: Radionuclides, clay mineral, pharmaceutical, cosmetic. 1. Introduction Clay minerals are used in pharmaceutical formulations as active ingredient or excipient. As active principle, clay minerals are used in oral applications as gastrointestinal protectors, osmotic oral laxatives and antidiarrhoeaics. Topical application includes their use as dermatological protectors and in cosmetics. It is also used in spas and aesthetic medicine 1 . The properties of the clay minerals, which made them appropriate for therapeutic uses, are fundamentally: a high specific area and adsorptive capacity, rheological properties and chemical inertness.