X-Ray:
A form of electromagnetic radiation with very high frequency and energy. X-rays lie between ultraviolet radiation and gamma radiation on the electromagnetic spectrum. It is used to investigate the manufacture of an object in particular sculpture, among other uses.
X-ray diffraction:
An analytical tool for identifying materials.
Find a more detailed description here.
X-ray fluorescence spectrometry (XRF):
A non-destructive analytical tool for identifying materials.
