X-ray absorption spectroscopy has become a common technique in mineral studies only in fairly recent times. It is an element-specific method which is suited to extend structure determination down to the local environment of an atom, i.e. a volume some three orders of magnitude less than that inspected by methods based on X-ray diffraction. However, in line with many other modern techniques, X-ray absorption spectroscopy is neither simple as for the practical operations by which one records high-quality experimental results, nor it is straightforward in the interpretation of them, the more so as minerals are far more complex multi-atomic systems than most compounds investigated by other material scientists. Consequently the mineralogical literature related to X-ray absorption spectroscopy is full of misunderstandings, which may even become traps for a new user. A further motive for the poor interpretation of experimental results that are otherwise technically excellent arises from the bare fact that the theoretical framework of X-ray absorption spectroscopy lies well beyond the basic physics normally taught to mineral and material science students. Indeed, this is possibly why quite a few people have used this powerful technique as if it were a black box (e.g. the ominous “fingerprinting” practice!), or they have overextended the interpretation of spectra beyond what is their true potential content (cf. Stern, 2001).

In this chapter, I try to show all what is possible as well as all what is reasonable to obtain by the main absorption spectroscopy methods in use at the present time