The application of mineralogical techniques to the study of pyrometallurgical products can provide important information that allows a better understanding of the reactions that occur within the furnace. The reactions can be deduced from the reflected light determinations of variations in mineralogical assemblages between, samples collected from different portions of the furnace and by the direct observations under reflected light of mineral textures in which one mineral is partly reacted to another. Compositional variations within mineral solid solutions can be quantitatively determined by electron microprobe analyses. Phase abundances within each sample can be quantitatively determined by automatic image analysis. By these techniques, small but important variations in mineral assemblages, phase abundances, phase compositions, and mineral textures can be distinguished between pyrometallurgical samples and related to differences in conditions of production.