A novelty for cultural heritage material analysis: Transmission Electron Microscope (TEM) 3D electron diffraction tomography applied to Roman glass tesserae

We present a novel electron diffraction technique (Automated precession 3D diffraction tomography - ADT) based on a Transmission Electron Microscope (TEM) to precisely determine unit cell parameters, Space Group symmetry and atomic structure of various pigment/opacifier crystallites of submicron dimensions and commonly present in colored Roman glass tesserae. Such technique can operate at nanometer scale and it is possible to distinguish even between mineralogical phases of similar/same chemical composition, but different crystal structures.