Blending of different types of coals is an economical method of utilizing locally available lower quality coals. Four blends of Wyoming/Oklahoma coal were prepared (100:0, 90:10, 75:25, 0:100) and burned in a laboratory furnace in a diffusion flame of a mixture of propane and nitrogen in air. Flame temperatures ranged from 1419 K for Oklahoma to 1626 K for Wyoming coal. The higher temperatures indicate better boiler utility, more oxidation, less free carbon, more and better quality fly ash. These observations conform well with the SEM evaluations which indicated that as the amount of Wyoming coal increased, the matrix contained densely populated glassy spherical particles. The SEM data on cured paste samples indicated that the Wyoming fly ash showed a better tendency to crystal (presumably ettringite) formation, followed by the blends of 90% Wyoming-10% Oklahoma and 75% Wyoming-25% Oklahoma. The least amount of crystal formation was observed in the fly ash of 100% Oklahoma coal. These effects are extremely pronounced in the early curing stages.