Weathering of Clay-Pyrite of Coal-Bearing
Formation in the Endemic Fluorosis Area
of Southwest China

It is common practice to use clay for coal-burning in fluorosis areas on the border of Yunnan, Guizhou, where coal-bearing strata is widely outcropped, and clay for coal-burning is usually considered to be collected from efflorescent clay in coal-bearing strata by some scholars. However, the relevant chemical properties of the clay, the mechanism that causes the fluorosis are not clear and the chemical forms of fluorine species present during transfer from the clay to the human body remain unclear. In this study, approximately 71 samples of efflorescent clay of coal-bearing strata were collected from seven counties in this area