Appl Phys A (2009) 94: 871–878 DOI 10.1007/s00339-008-5018-9 Dating study of two rock crystal carvings by surface microtopography and by ion beam analyses of hydrogen T. Calligaro · Y. Coquinot · I. Reiche · J. Castaing · J. Salomon · G. Ferrand · Y. Le Fur Received: 30 April 2008 / Accepted: 24 November 2008 / Published online: 18 December 2008 © Springer-Verlag 2008 Abstract Two artefacts made of rock crystal (quartz) from the collection of the Musée du quai Branly in Paris, France, a skull approximately half of the size of a real cranium and a smaller anthropomorphic head, purportedly attributed to pre-Columbian Mesoamerican cultures, were studied to as- sess their authenticity. The surface of the artefacts were ex- amined by means of optical microscopy and scanning elec- tron microscopy (SEM) and were analyzed nondestructively by ERDA (Elastic Recoil Detection Analysis), an ion beam analytical method that can measure hydrogen concentration profiles in depth. Optical and SEM imaging of tool marks indicates that the skull has been cut from a rock crystal block using machine lapidary techniques unavailable to pre- Columbian artisans, whereas the anthropomorphic head has more likely been carved and polished with manual tech- niques comparable to ancient ones. Hydrogen depth profiles in the first micron below the surface of the artefacts have been measured by ERDA with a 3-MeV He beam in a con- trolled helium atmosphere. Recently the progressive pene- tration of water at the surface of a quartz sample exposed to the natural environment has been proposed as a dating method (labeled quartz hydration dating or QHD) applica- T. Calligaro ( ) · Y. Coquinot · I. Reiche · J. Castaing · J. Salomon Centre de recherche et de restauration des musées de France—C2RMF, CNRS UMR171, Palais du Louvre, 75001 Paris, France e-mail: thomas.calligaro@culture.gouv.fr G. Ferrand Ecole nationale supérieure des mines de Paris, 75006 Paris, France Y. Le Fur Musée du quai Branly, 75007 Paris, France ble to archaeological artefacts made of this material. The shallower penetration of H clearly indicates that the rock crystal skull was manufactured more recently than the refer- ence quartz sample cut in 1740. As for the anthropomorphic head, the deep penetration profiles indicate an older arte- fact. Thus the converging micro-topographical examinations and hydrogen profiles of the samples surfaces indicate that the skull is probably not a pre-Columbian artefact but has been carved in the 18th or 19th century. The anthropomor- phic head, on the other hand, could have been carved in the pre-Columbian period. In addition, the ERDA method car- ried out with an external beam presented here provides a new and simple approach for the nondestructive authentication of quartz-based archaeological artefacts by QHD. PACS 61.72.Ww · 81.05.Je · 81.70.Jb · 82.80.Yc 1 Introduction Many rock crystal skulls carved before the middle of the 20th century are claimed to be artefacts manufactured by pre-Columbian Mesoamerican cultures, although none has been retrieved from a documented archaeological excava- tion. Among the around ten large quartz skulls that appeared before 1930, three famous ones are conserved in museums, namely the British museum in London, the Smithsonian Institution in Washington, and the Musée du quai Branly in Paris, the others being in private collections. Whereas Mesoamerican art has numerous examples of skulls made of stone, such quartz skulls have little stylistic or technical re- lationship with these genuine archaeological artefacts. Jane Walsh, anthropologist at the Smithsonian Institution, who has long been investigating these skulls from both biblio- graphic and scientific points of view, has cast serious doubts