ChileanJAR

From the principal phosphate field of Chile, Le. Mejillones (23°06'S; 70º27'W), Bahía Inglesa (27º04'S; 70º49'W) and La Serena (30º20'S; 71º22'W) representative samples were characterized chemically and mineralogically in order to evaluate its suitability for direct application. The phosphoric constituent of rocks from Mejillones and Bahia Inglesa is carbonate-fluorapatite including accessory minerals. Apatites from both places of sedimentary marine origin have a high degree of isomorphic substitution of phosphate by carbonate. The phosphoric constituent of the rock from La Serena is dominantly chlorapatite of igneousjmetamorphic origin, induding hydroxyapatite and other accesory minerals. Chemical composition of the rocks is variable; the content of P₂O₅ reaches 33.0%, 18.4% and 5.0% in rocks of La Serena, Bahia Inglesa and Mejillones respectively. Solubility index indicate that rocks from Bahia Inglesa and Mejillones are highly reactives, but not the one of La Serena, which shows a very low reactivity degree. Chemical composition and reactivity qualify the phosphoric rock of Bahia Inglesa as a very reactive phosphorite, with evident potential fertility capacity. In referance tothe rock of Mejillones although its high reactivity, the low contents of P₂O₅, about 5%, limited the use of the rock. The rock of La Serena has not option of direct application. Phosphoric rocks could be an interesting option of fertilizer use for chilean soils, particulary for volcanic ash soils with pH below 6.0.