Patrick Degryse is Professor of Archaeometry at KU Leuven, studying the history and use of mineral resources in ancient technology. Julian Henderson is Professor of Archaeological Science at the department of Archaeology, School of Humanities, at the University of Nottingham, UK. Greg Hodgins is an Assistant Research Scientist and an Assistant Professor of Anthropology at the National Science Foundation - Arizona Accelerator Mass Spectrometry Laboratory, University of Arizona, Tucson, AZ, USA.