Nuria Lázaro Milla, 2017

In 2014, samples taken from the two sculptures the study of which is presented
in these pages were sent to the Research Reactor Center of the University of
Missouri, where they underwent instrumental neutron activation analysis (INAA),
a radioactive procedure used to determine the concentrations of elements that
integrate a material. After comparing the results with more than 2,300 profiles
registered in the database of The Limestone Sculpture Provenance Project, it was
concluded that their composition coincided largely with the limestone found in
quarries and monuments of Île-de-France, a similarity percentage that increased
significantly in the comparison with fragments originated from or related to the
cathedral of Notre-Dame de Paris.