We use MODIS Terra Level 1B data containing calibrated and geolocated radiances to investigate a regional signature of wind-blown mineral dust in the thermal-IR. MODIS data over oceans for the 2000--2004 time period were examined for the presence of dust plumes that originate from the main dust sources located in East and South Asia, Middle East, Northern Africa, and Australia. A number of representative cases for different source regions were selected and analyzed in terms of brightness temperatures at three IR channels centered at 8.55, 11.03, and 12.02 ¿m. The distinct differences in the thermal-IR signature of atmospheric dust for the considered regions were found. Our analysis indicates that these differences are likely due to different mineralogical composition, although other factors (e.g., multilayered vertical distribution) may be also involved. Implications of our findings to the detection of dust based on the techniques using brightness temperature differences are discussed.