Comment by tbensky

XRF=x-ray fluorescence. You shoot X-rays into a metal, typically the gamma rays from an Am-241 source. This causes atoms in the metal to fluoresce their own gamma rays that are a (somewhat) unique signature of the atom itself. So in sum, XRF allow one to non-destructively determine the atomic constituents of a bulk material (but 'heavy' materials..heavier than Silicon for example).