Leonardite is a naturally oxidized lignite characterized by high percentages of humic acids. Visual inspection is usually insufficient to distinguish leonardite from lignite. The low-angle X-ray scatterings from 8-2.5A degrees of lignite, leonardite and humic acids were analyzed. The primary subpeak shifts from 3.37A degrees for leonardite to 3.44-3.58A degrees for lignite and vitrinite. Leonardite and lignite can also be distinguished by examining the relative intensities of the 3.1-3.7A degrees sub-peak.