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In X-ray fluorescence a specimen is bombarded by a beam of x-rays from an x-ray tube or radioactive source. These x-ray displace electrons from the inner orbits of the constituent atoms. These spaces left by these displaced electrons are filled by electrons from the outer orbits. The energy released by this process is emitted by a secondary or “fluorescent” x-ray. The energies of the secondary x-rays are characteristic of individual elements in any given material. Depending on the configuration of the equipment, X-ray Fluorescence can identify about eighty elements simultaneously.
X-ray Fluorescence can be conducted on small objects with virtually no sample preparation. X-ray Fluorescence has been applied to a wide range of archaeological materials including obsidian, pigments, ceramics, metals and chert for the purpose of identifying sources and also for identifying unknown materials.
X-ray Fluorescence is a semi-quantitative technique. Samples are ground into a fine powder that can be analyzed. Analysis of standard materials can also improve analytical accuracy. The output of the analysis is a table that delineates the elements observed and their relative quantities.
As mentioned earlier, X-ray Fluorescence analysis is a semi-quantitative technique. X-ray Fluorescence lacks the precision of other elemental analysis techniques such as Neutron Activation Analysis. That is, the data produced by most analyses cannot be treated statistically or reproduced consistently within the same sample. However, for most routine archaeological analyses X-ray Fluorescence is good enough to distinguish most obsidian sources from one another, identify the elements in pigments and metals, and distinguish different sources of pottery and chert