Chemical, physical and structural characteristics of apatites are very important to know in order to evaluate the potential use of phosphate rocks in agricul-tura. Results of researches, most performed in the National Fertilizer Development Center (TVA), Alabama, USA, have developed a lot of analytical technics for row phosphate materials characterization.

Correlation established between chemical and instrumental data make possible to estimate, rapidly and accurate, the type of apatite of a particular ore. Measurement of unit-cell parameters, and it relation with “CO, Index” obtained by IR-spectroscopy, allow to estimate the degree of CO, substitution in apatite.

Between the “CO, Index” and the ratio CO;: PO, there is a direct weigh relationship which is independent of concentration effect of apatite. As a preliminary screening, IR data together with X-ray characteristics and chemical analysis could be related to the reactivity of phosphoric rocks and with it probably agronomic effectiveness.