This articles describes investigations carried out by the authors of the mineralogical and physico-chemical behavior of clays upon refiring. Results of the experiments are intended to aid interpretation of archaeological ceramics of the 3rd millennium B.C. from Abu Dhabi. Emphasis is placed on the changes in calcium carbonate upon firing. Although these changes provide, in theory, an a posteriori thermometer, a number of complications exist. Other minerals, for example, green hornblende and olivine, also go through transformation upon heating, and these can also be used to estimate firing temperature. The problem of rehydration of calcite is discussed briefly. Color of a fired ceramic is discussed as well: it is stressed that fired color depends on relative proportions of Calcium, Iron, and Aluminum, and on the firing temperature and atmosphere. The importance of firing suggests that composition cannot be estimated simply from color. A final study shows that comparison of major and minor element compositions can give erroneous indications of where ceramics might have come from. Provenance studies thus should employ microscopy and/or trace element analysis in addition to major and minor element analysis.