FINGERPRINTING POTTERY WITH X-RAY FLUORESCENCE CHEMISTRY

Chemical and isotopic signatures have been widely used to provenience geological and archeological materials. Traditionally wet chemistry analysis had to be performed to obtain compositional information. XRF-based methods are advantageous due to their non-destructive nature and rapid data collection. Scans can be performed on various spots of an artifact for validation. In this study, a portable XRF Environmental Analyzer (Delta Classic, Innov-X) was used to examine late 18^th century pottery fragments found at City Hall Park of New York City, as well as Raeren stoneware that is known to originate from Germany. It is reasonable to assume that there was only very limited producers of such potteries during that time period. Therefore the clay likely can be traced back to few sources. Three types of surfaces were analyzed: unglazed surfaces likely reflect the composition of clay material; glazed surfaces are more controlled by the salt used; while the ink is known to be a different material that often contains heavy metals (such as cobalt) that give color. Rb-Sr ratio appears to be a reliable parameter to distinguish stoneware originated from New York City or Germany. For samples from NYC, Unglazed (n=11) surfaces gave Rb-Sr of 1.54±0.16, while for glazed surfaces (n=11) and the ink (n=19) this ratio is 1.28±0.16 and 0.56±0.28, respectively. For samples from Germany (n=3), both unglazed and glazed surfaces showed an Rb-Sr ratio of lower than 1. Our preliminary results indicate that chemistry data obtained by portable XRF scanner may be a promising tool for the provenience of potteries (a.k.a., ceramics). There are many collections of ceramics that can potentially be scanned, and a database can be established without involving high cost.