Phosphate rock sedimentary apatites

Our study of sedimentary apatite from Israel proved that laser-induced time-resolved luminescence is a perspective tool for evaluation of sedimentary phosphate ores with high dolomite content (Gaft et al. 1993b). The idea was based on the fact that natural apatite contains several characteristic luminescence centers, which enables us to differentiate it from dolomite. The most widespread characteristic luminescence center in sedimentary apatite is uranyl (U02) with a typical vibrational green band luminescence under nitrogen laser excitation (Fig. 8.13a,b). Nevertheless, it appears that such luminescence is absent in phosphate rock samples from Florida, evidently because of extremely low uranium concentration (Fig. 8.13c,d). hi order to find potential liuninescence centers, ICP-MS analyses of Florida phosphates was accompHshed. From discovered REE, theoretically Dy + is the best candidate... 

Sedimentary phosphate rocks that are obtained from. insular and cave deposits often contain carbonate apatites that have a lower F content than that of stoichiometric fluorapatite and, according to calculations, contain significant amounts of hydroxyl in their structures. Although some of these carbonate apatites may meet the francolite definition, they have crystallographic, chemical, and other physical properties that differ substantially from those of francolites that contain excess fluorine [7]. These carbonate apatites form a series with end members that contain almost no fluorine (carbonate-hydroxylapatite) (Table 5.4) and end members that are very close in composition to pure fluorapatite and francolites that have almost no carbonate substitution. Members of this series are referred to as hydroxyl-fluor-carbonate apatites in this section. Table 5.5 shows the a-values of some phosphate rocks containing hydroxyl-fluor-carbonate apatites in this series. 

Phosphate rocks from the same sedimentary deposit may contain apatites with widely differing properties due to geologic conditions and posfriepositional alterations... 

The determination of the type and amount of apatite, in a phosphate rock is very important. Sedimentary phosphate rocks containing the most highly carbonate-substituted apatites can only be beneficiated to maxi-mumrgradesrofr33-34 wt % P2O5. Depending on the amount of carbonate substitution, the grade can increase to a maximum of about 42 wt % P2O5 for sedimentary apatites with essentiaDy no substitution. In order to reach... 

Lehr and McClellan [17] studied a suite of sedimentary phosphate rocks and an igneous phosphate rock concentrate and concluded that carbonate substitution in apatite was the dominant factor influencing reactivity measurements. This study also concluded that reactivity... 

The Kola deposits, operated by P.O. Apatit, formed the core of FSU phosphate rock and fertilizer production capabilities. In 1989, P.O. Apatit produced about 20 million tonnes of phosphate rock [661. The P.O. Apatit production estimate for 1993 was about 8.5 million tonnes. Due to the drop in demand and to rationalization and privatization, mines and several processing plants have been closed. The downturn of the Kola industry (and Russian economy) is also intimately intertwined with FSU sedimentary phosphate rock production and the fertilizer industry based on this rock. The production of many fertilizer plants in the P U used high-quality phosphoric add feedstock produced from Kola apatite and locally obtained lower grade sedimentary phosphate rock to produce off-grade TSP products. 

Mineralogy of Sedimentary Apatites and the Relationship to Phosphate Rock Reactivity, Paper presented at the National Workshop on Fertilizer Efficiency. Cisarua, Indonesia, November 12-13, 1990.. ... 

The commonest concentrated igneous apatite deposits consist mainly of fluorapatite, Ca,o(P04)6F2, but isomorphous chlorapatite, CamCPO igClj, and hydroxyapatite, Caio(P04)6(OH)2, are also found in close association or in solid solution (Chapter 5.1). Apatite occurs mostly as a sedimentary deposit with an approximate composition Caio(P04)6F2, which is named Phosphorite or "phosphate rock. Collophane is a term sometimes used to describe varieties of cryptocrystalline phosphorite which are fine grained and optically isotropic. 

Apatite also occurs (less abundantly) as igneous phosphate rock which is highly crystalline and much purer than sedimentary phosphorite. Commercially important igneous rock formations of crystalline fluorapatite are found in the Kola peninsula (Khibiny) of Russia, South Africa (Palabora), Brazil (Jacupiranga) with smaller deposits in Uganda, Finland, South Norway and South Sweden. All these deposits, however, at present account for less than 15% of the world total of mined apatite. 

Phosphorites are sedimentary rocks that contain at least 15-20 wt % P2O5 (Boggs, 1995), 266. The phosphate in phosphorites primarily occurs as apatite (Ca5(P04)3(F,Cl,0H)). Typically, phosphorites chemically precipitate in deep, cold marine waters. Due to chemical similarities, arsenate may partially substitute for phosphate and the arsenic concentrations of phosphorites may exceed 100 mg kg-1 ((Matschullat, 2000), 299 Table 3.23). However, arsenic concentrations in some phosphorites (e.g. southeast Jordan) are relatively low (7-9 mg kg-1) and the arsenic is mostly associated with clay and carbonate minerals rather than phosphates (Al-Hwaiti, Matheis and Saffarini, 2005). 

Apatite A phosphate mineral (ideally, Ca5(P04)3(F,Cl,0H)) that may occur in sedimentary, metamorphic, and igneous rocks. Arsenate may substitute for phosphate. 

Fluorine occurs exclusively as the fluoride anion, F , in soils, where it complexes strongly with metals such as and Fe ". It is found in structures of hydrous minerals, isomorphously substituting for structural OH . Thus, F can be found in micas, amphiboles, layer silicate clays, apatite (rock phosphate), and numerous other minerals. Because it is associated with clay structures, the natural concentrations of fluorine in fine-textured mineral soils and sedimentary rocks can be high. 

Fertilizer and Minerals for Industry. Fertilizers contain minerals that have nitrogen, phosphorus, potassium, and a few other elements necessary for the growth of plants. In Peru, deposits of guano (seabird excrement), which is rich in these elements, have been mined and used as fertilizer. Saltpeter (potassium nitrate) has also been mined in Peru. A calcium phosphate mineral, apatite, occurs in some sedimentary rocks, so some of these have been mined for the phosphorus. 

Reserves Large resources of yttrium in monazite and xenotime are available worldwide in ancient and recent placer deposits, carbonatites, uranium ores, and weathered clay deposits (ion-adsorption ore). Additional large subeccaiomic resources of yttrium occur in apatite-magnetite rocks, deposits of niobium-tantalum minerals, nonplacer monazite-bearing deposits, sedimentary phosphate deposits, and uranium ores. The world s resources of yttrium are probably very large [39]. 

---