This Bureau of Mines report describes the results of scanning electron microscopic (sem) studies of the combustion residues of carbonaceous dust particles resulting from explosions and thermal ignitions in laboratory and full-scale mine tests. The dusts studied varied widely in rank and volatility: Pittsburgh seam bituminous coal (35% volatility), Pocahontas seam bituminous coal (16% volatility), anthracite (7% volatility), graphite, and diamond. The most systematic explosion studies were performed in an 8-l chamber with narrow size distributions of Pittsburgh coal dust with surface mean diameters of 2, 22, and 84 um. Experiments were conducted mainly in air, with some data obtained in 50% 02. Oservations of the bituminous coal explosion residues showed particles with rounded edges, particles with blowholes, and some cenospheres. The lower volatility dust residues showed fewer changes from the original, unburned dust. In addition to the experimental studies, results of sem observations of residues from a mine explosion disaster are reported.