A linear mixture model was applied to Landsat Thematic Mapper data to map iron-oxide content over the northern part of the Namib Sand Sea, Namibia. Field samples were collected to calibrate the remotely sensed iron oxide proportions to dithionite extractable Fe in mg g−1, the in situ proportions correlating strongly with the remotely sensed estimates (r=0.91). The results reveal a region of high Fe-oxide concentration in the east, an area of low Fe-oxide concentration in the west, separated by a mixing zone. We interpret this to indicate that there is more than one sand source contributing to the sand sea.