Millions of tons of ash and slag are produced each year as a result of energy production. This study looks at the mineralogy and textures in the ash resulting from the gasification of a 25% Passaic Valley sewage sludge, 75% Pittsburgh #8 coal slurry in a Texaco gasification facility and at ash resulting from the incineration of municipal solid waste at several facilities in Virginia and North Carolina. This information is then compared with similar studies done on ash and slag from coal-burning power plants and a study done on petroleum coke slag which was produced at a Texaco gasification facility. Lastly, a comparison of bulk chemistries of ashes to those of soil and crustal rocks is made. A general understanding of the stability of elements, especially metals, in terms of the phases in which they are contained as well as the textures, was hoped to be gained from this study. Samples for this study were polished sections which were 2.54 em in diameter that were set in cold-setting epoxy then ground and polished. Samples were then studied under a reflected light microscope before being carbon coated for study on a SEM and an electron microprobe. Photos of textures and analyses were made throughout. At least 50% of the ash from all sources was a Si-Al oxide rich glass which had varying amounts of Fe, Ca, K, P, Mg, and Ti and other trace elements. Fe oxides and spinels were common phases found. Pb and Zn were rarely encountered, but were found as both oxides and sulfides. Cr was found in the form of spinels, often covered by a protective AI enriched outer rim. The heavy metals found were successfully bound as mineral analogs or as a glass phase. The only phase found to be reactive was an AIC matrix containing subhedral SiC crystals. The AI phase effervesced when placed in contact with water, changing from tan to greenlblue/violet in color, releasing a gas (probably CO₂, C2H2, or CH4) in the process. / Master of Science