New Mexico Geological Society Annual Spring Meeting — Abstracts

This research explores what mineralogical differences in clays account for their performances as slip clays in the production of Native American traditional ceramics. Slips are thin suspensions of clay in water applied to the entire surface of a clay vessel before firing and serve as an adhesive base for painted designs. Organic paints adhere to some of these clay slips during firing, but others do not. The clays for this study are derived from fluvial mudstones in the Eocene Diamond Tail Formation in the Galisteo Basin, north-central New Mexico. Random samples were collected within massive, bioturbated, floodplain mudstone facies where the clay mineralogy can vary significantly over short distances. While there are multiple variables to be considered, this research focuses on evaluating what mineralogical differences in the clays could account for their function as slips and how the mineralogical differences relate to their geological origin. Mineralogical variability can result from primary depositional variations and/or effects of Eocene floodplain weathering. X-ray diffraction was used to assess the chemical composition of the clay samples and to interpret the possible causes of the performance differences. Preliminary results suggest that slip clays containing a larger smectite to illite ratio retain an organic paint better than those clays with relatively less smectite.