REGENERATION OF ORIGINAL CLAY MINERAL COMPONENTS IN ANCIENT MAYA CERAMIC WARE TO DIFFERENTIATE INDIGENOUS VERSUS TRADE WARE ITEMS USING XRD ANALYSIS

Important evidence confirming exchange of cultural information and tradeware items among civilizations existing in pre-Columbian times can be established by detailed analysis of the mineral constituents found in ceramic objects at different sites in the Americas. Specifically, the mineralogy can often document whether a particular object was produced using materials that are indigenous to a certain area or whether the object is likely (or definitely!) tradeware from a distant population or ceremonial locale. Typically, ceramic objects (pottery, urns, figurines, etc.) were manufactured by high temperature “firing” of objects in kilns at temperatures of 300 ^oC, or higher, to which rock fragments, shells, pottery fragments, etc. (known, collectively, as “temper”) were added to prevent the clay from cracking on cooling. Unfortunately, once fired, most clay minerals lose their identity because of collapse of the phyllosilicate lattice. Their former identity, however, is important because the original clay minerals may be diagnostic of a specific ”manufacturing locale”. Recovery of the clay’s original identity, fortunately, can be obtained by pulverizing a small fragment of the ceramic material and heating it to a temperature in excess of 1,100 ^oC for a period of approximately 2 hours, followed by rapid quenching of the sample. The elevated temperature permits recombination of ions to form new, high temperature phases (such as mullite, cristobalite, enstatite, spinel etc.) that are identifiable by subsequent XRD analysis of the sample. As such these serve as “fingerprints” for the original clay mineral phase(s). As an example, using this method, Maya ceramic ware from manufacturing sites in northernmost Yucatan (Mexico) have been identified from locales as distant as Central Guatemala, as well as southern Honduras.