Previous analysis of ash generated during coal gasification using a high calcium coal (SUFCo) suggested that iron sulfide was the dominant sulfide species in the system. During a recent analysis of ash material removed from a gasification pilot unit using Pittsburgh No. 8, a high iron coal, sub-mu m to 5 mu m euhedral iron sulfide crystals were identified on the outer surface of the ash. X-ray diffraction suggests both pyrrhotite and troilite were present in the ash. No other sulfides were identified. Within the iron sulfide crystals were siliceous fly-ash particles. Possible modes of formation which include vapor deposition, accumulation and annealing of fume particles, or recrystallization of iron sulfide droplets were investigated.