The aim of this study is to find a tracer allowing retrieval of the regional origin of mineral dust for Saharan aerosols transported over the North Atlantic Ocean. Because of physical and chemical fractionation processes occurring at the soil-atmosphere interface and during the atmospheric transport of dust, clay mineral species seem to be the best candidate. This study shows that the ratio between relative abundance of illite and kaolinite (I/K ratio) is the parameter that is the most sensitive to the regional origin of Saharan dust collected on Sal Island (Cape Verde). By comparing the I/K ratio measured in dust emitted from the same Saharan source and collected along its transport both on Sal Island and Barbados (Caribbean Sea), we show that this ratio seems to remain unchanged after long-range transport. ¿ 1998 American Geophysical Union