The text which follows is based largely on the personal experience of the authors. The examples used which concern archaeological material, thin sections of sherds and many of the case studies are for the most part those which we have developed ourselves. This experience. may seem biased when one thinks of the large experience of petrographic archaeology, and this is surely true, but it is a reflection of our observations which are more complete for the objectives we have in mind than most of the examples given in the literature. For example, we have access to initial sherds, photo- graphs,...