The Kelso dune field is located in the eastern Mojave Desert, California, at the terminus of a sand-transport pathway, which has its primary source at the Mojave River Wash 50 km to the west. Initial examination of 1984 airborne thermal infrared multispectral scanner (TIMS) data showed significant spectral variations that indicate potential mineralogic heterogeneities within the active dunes. This result prompted the collection of a suite of 48 sand samples in 1990, and the acquiring of new TIMS data in 1995. This new data set was used to test a newly developed linear spectral retrieval algorithm in conjunction with a spectral library of end-member minerals. Results of this analysis produced images of end-member minerals that showed marked variations within the dunes. In addition, standard petrographic techniques revealed that the dunes contain mineralogic variations and were much less quartz rich (∼42%) than previously reported (∼70%–90%). Point-count results agreed with the spectral data to within an average of 5.3% for TIMS-derived and 3.1% for laboratory-derived mineralogic abundances. High concentrations of several of the end-member minerals on the surrounding alluvial fans indicate a potential nearby source for these minerals. Most evident is the presence of potassium feldspar from the fan that emanates from the Providence Mountains east of the dunes. This previously unidentified potential sand input is not visible with other remote sensing techniques and was confirmed with additional field sampling. Much of the quartz and some plagioclase feldspar, however, appear to have been transported from the Mojave River Wash source as previously reported. This study also validates the potential of using thermal remote sensing from future satellite-based instruments to globally monitor desert fringe areas susceptible to the changing conditions of sand encroachment.