Mineralogical characterization of commercial clays used in cosmetics and possible risk for health

Abstract

The present study was carried out to determine the suitability of 15 clay samples used for cosmetic purposes. The mineralogical composition of both the bulk sample and the clay fraction was determined by X-ray powder diffraction, and the bulk chemical composition was also obtained by energy-dispersive polarized X-ray fluorescence spectrometry, with particular focus to the trace elements to assess the possible risk for health.The bulk mineralogical composition of the studied clay samples is characterized by the presence of a significant non-clay fraction made up of calcite and quartz, with minor dolomite, feldspars, and gypsum. The clay fraction is composed of illite, smectites, interstratified illite/smectite, kaolinite and chlorites in variable amounts and diverse associations. The most represented samples are green clays which are composed of interstratified illite/smectite+illite+chlorites, with considerable amounts of Ni and Sr, while the other green samples are composed of illite only and are enriched in As. The almost pure smectite samples (both brown and white in color) are depleted of almost all trace elements and, therefore, represent the most suitable samples for commercialization. In contrast, the white kaolinite-rich sample is notably enriched in Zn, As, Ba and Pb, and is thus the most potentially hazardous product for human health.