The aim of this paper is to survey the achievements in the field of crystallochemistry of natural phosphates and the application of the results obtained to phosphate technology. The absolute majority of phosphate minerals belongs to the apatite group with the ideal formula Caio(P04)6F2.It is shown that every atom in the real structure of apatite is characterized by at least two non-equivalent crystallochemical positions. The crystal lattice of phosphate is dynamic. Energetic treatment of apatites results in the relocalization of anions from one structural position into the other. Distribution of various ions between their non-equivalent structural positions is of great importance to mineral properties. Crystallochemical analysis facilitates the prediction of mineral properties, prevention of technological failures and optimization of phosphorites processing.

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The thermal transformations in phosphorites during flash calcination were investigated by FT-IR spectroscopy, X-ray diffraction and chemical analyses. During flash calcination changes occur, both in the composition of the phosphorite and in the crystallochemistry of the fluor-carbonate-apatite (francolite). The former changes include: decomposition of a great part of the calcite in the rock and oxidation of organic matter. The latter changes include: partial removal of the structural carbonate; partial relocation of the remaining carbonate ions in the apatite structure; a new arrangement of hydroxyl groups and fluorine on the hexagonal axis; partial condensation of the orthophosphate groups and increase of crystallite sizes. Isomorphous substitution ofPO43 in apatite by SO42 and SiO44 may take place.

Studies by XRD and FTIR analyses of the structure of Sokli and Siilinjärvi apatites and a comparison with the Kola and Kovdor apatites are presented. In the structure of apatites from Finland the occurrence of F...OH and F...OH...F bonds and the incorporation of CO, 2 ions into A and B positions were established.

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