The mineralogical, micromorphological, geochemical and crystallographic characteristics of the different types of apatite from the Catalão I alkaline-carbonatitic complex, Goias, Brazil, were determined by optical and scanning-electron microscopy, electron-microprobe analysis, Raman micro-spectroscopy, X-ray diffraction, thermodifferential and thermogravimetric analyses and Fourier-transform infrared spectroscopy. There are three main generations of apatite: igneous, postmagmatic or hydrothermal, and supergene. The composition of apatite of each generation has been determined. Data from primary apatite affected by weathering processes show compositional changes prior to the total destruction of grains. The main geochemical trends observed from the first to the third generation are: a) increase in CO 3 2-(that replaces PO 4 3-), in F (which follows the incorporation of carbonate), in Ca (owing to loss of substituting cations, mainly Sr, Na, and REE) and in the ratio CaO/P 2 O 5 (increase of Ca due to loss of the cations that substituted for Ca, and decrease of PO 4 3-, partially replaced by CO 3 2-), b) decrease in Si and P (replaced by C), in Sr, Na and REE (replaced by Ca) and in analytical totals (owing to an increase in components not detected using the electron microprobe, such as C and OH). These chemical changes, along with contemporaneous modification of the morphology of the apatite grains, contribute to an undesirable behavior of the apatite ore, once submitted to processes of industrial concentration. The types of apatite and the processes of their formation here defined and established for the Catalão I alkaline-carbonatitic complex are quite common and widely distributed in all carbonatitic phosphatic raw materials in Brazil, as observed in previous studies. The coexistence of these morphological and compositional varieties is responsible for the heterogeneity and complexity of these ores.
