X-ray fluorescence is an analytical technique that returns information about the elemental composition of a sample. The sample is illuminated with an X-ray beam and the atoms which are struck by the beam emit X-rays in response, usually at several different energies. Different elements produce different distributions of emitted X-rays so the spectrum of emitted X-rays can be used to identify which elements are present in a sample.
Until quite recently XRF machines were sealed bench-top units which often required that samples be removed from an museum object for analysis. Portable XRF instruments can be taken to the object and used to analyze its surface without removing sample, but at a cost of less precise quantitative measurement.
This canoe prow from the Solomon Islands has unusual decoration: pieces of glass inset below the ears rather than the more usual pieces of shell. Glass was not produced in the Solomon Islands when this object was made; pXRF analysis of the glass shows that it could have been made in Europe, the Americas, or Asia.
This rubbing scroll from China was made with a red ink, The ink had been listed as 'vermilion' which is a mercuric sulfide, but pXRF analysis shows that there is no detectable mercury in the ink and the red color is a lead pigment, probably red lead oxide.