On the Nigerian Jos Plateau tin mining is extensively carried out in open pit style. Several types of materials occurring there (raw materials, waste, and soil) were analysed radiometrically. The geochemical host phases of the natural radionuclides were determined by a sequential extraction procedure according to the European BCR standard. It was found that especially easily mobilisable (228)Ra must be taken into consideration as a radioactive contaminant for the mining area.