The analysis of individual clay-sized particles by energy dispersive X-ray spectroscopy in a transmission electron microscope and particle characterization by appropriately selected X-ray intensities ratios allow fast identification of a large number of particles. The method allows identification of various minerals, notwithstanding a relatively wide range of X-ray intensity ratios of individual mineral particles. Under average working conditions, ten to twenty mineral particles can be analyzed per hour. For every case suitable standards must be selected, a statistically meaningful number of particles analyzed and appropriate X-ray intensity ratios determined, calculated and used as data input in the analysis of clay-sized sediment particles. The method was applied successfully to a detailed study of particles from Lake Erie bottom sediment. The mineralogy of Lake Erie sediments and that of its drainage basin was roughly known.