Evaluation of segregation in Roman sestertius coins

Three brass sestertius coins from the reign of Gordian III were imaged at the Oak Ridge National Laboratory’s neutron imaging beam, CG-1D, at the High Flux Isotope Reactor. Tomography results showed a gradual variation in neutron attenuation from one side of the coins to the other or toward the center of the coin. Linear neutron attenuation values calculated from the neutron radiographs, as well as micro-XRF results, suggest that this gradual variation in neutron attenuation is associated with elemental segregation within the coins. The difference in segregation patterns between the coins implies two types of casting methods were utilized to form the coins—vertical and horizontal casting methods.