ABSTRACT
Crystalline or amorphous, biominerals always comprise mineral and organic fractions, whatever the mineralogy. Chemical compositions are known using atomic absorption, and inductively coupled plasma with good precision. To investigate the composition and chemical specicity of biominerals, x-ray absorption spectroscopy and microspectroscopy are very attractive tools, which can provide information both on their mineral and organic components. Absorption edge spectroscopy techniques are based on the measurement of the absorption coeffcient variation by tuning the energy of the probing photons through an absorption edge of an element. The energy position of the absorption edge and the shape and position of the pre-edge peaks depend on the oxidation state and the geometry of the coordination sphere of the absorbing atom. The energy position of the absorption edge is usually taken as the inflection point of the main absorption jump, identified from the derivative of the spectrum.
