PIXE analysis of the obsidian support of two paintings from<br />the Louvre by Murillo

The very unusual black backings of two paintings by the Spanish master Murillo (1617-1682) representing Passion Scenes, on display at the Louvre museum, have been analyzed by PIXE with the AGLAE facility of the C2RMF. The support proved to be obsidian, a natural volcanic glass widely employed to produce archeological artefacts, in particular in South and Meso-America. Five archeological artifacts with similar shape to the paintings called “obsidian mirrors”, originating from Mexico and belonging to the collections of the Mus´ee de l'Homme in Paris, have been analyzed and the composition of four of them showed to be very similar to Murillo's obsidians. The comparison with the results obtained on reference obsidian samples from Mexican sources and with data from the literature by instrumental neutron activation analysis (INAA) suggested that the Ucareo/Zinap´ecuaro, Michoac´an, Mexico is the source of the obsidian employed for the paintings. A field trip to this area was therefore organized to collect samples whose natural slab shape and chemical composition confirmed the Ucareo provenance hypothesis. The rectangular backing of Murillo's paintings are unlikely archaeological artefacts but rather objects specially made after the Spanish conquest by Mesoamerican craftsmen, among which some were exported to Europe where Murillo spent all his life. The observation, in the walls of the church and other Christian monuments in Ucareo, of obsidian inlays, a material of particular significance in the pre-Hispanic culture, underlines the complex intrication of native culture and European influences which are also carried by Murillo's paintings. Meanwhile, a third painting on obsidian by Murillo as been identified in the Museum of Fine Arts of Houston, Texas, U.S.A. This study also points out that even if the ranges of elements dosed by PIXE and INAA do not fully overlap, the measurements obtained by both techniques can be efficiently used for provenancing obsidians objects