The mineralogy of suspended sediment in the Scioto and Olentangy Rivers was determined by x-ray diffraction methods. The mineralogy of the respective sediments from the two rivers reflects the bedrock lithology underlying each river quite well. The percentage of carbonate minerals was appreciably greater in the sediments of the Scioto River, while clay minerals are more abundant in the Olentangy River. Certain minerals may have been derived from the glacial overburden in this area. Talc was found to be the dominant constituent of the sediments in both rivers and its presence can be attributed to the use of pesticide powders in the drainage basin. Samples of pesticide powders were x-rayed for comparison with the sediment. Two (PHALTAN and BAYGON) showed a strong diffraction spectrum for talc, suggesting the distinct possibility that talc in the suspended sediment of the Olentangy and Scioto Rivers may be derived from pesticides.No embarg