Apatite phosphate

The major minerals that contain REOE include apatite, phosphates, sfen, perovskite, eudialite, pyrochlore and ortit, some of which contain significant quantities of REOE. 

The estimation of the crystallinity index (Cl) of bone is based on one of the four vibrational modes associated with the apatite phosphate group. In amorphous calcium phosphate, the absorption band at 550-600 cm-1 appears as a single broad peak, whilst in hydroxyapatite it is split into bands of unequal intensity by the apatite crystal field (Sillen and Parkington 1996). Based on the splitting factor introduced by Termine and Posner (1966), Weiner and Bar-Yosef (1990) proposed the use of a crystallinity index to measure the crystallinity of bone mineral. As illustrated in Fig. 4.7, the Cl is estimated by drawing a base line from 750 to 495 cm 1 and measuring the heights of the absorption peaks at 603 cm-1 (measurement a), 565 cm 1 (measurement b) and the distance from the base line to the lowest point between the two peaks (c). Cl is calculated from the formula ... 

Solubility product constant of calcium hydroxy apatite phosphate... 

Sery A, Manceau A, Greaves GN (1996) Chemical state of Cd in apatite phosphate ores as determined by EXAFS spectroscopy. Am Mineral 81 864-873... 

The interaction of the column anions suggests that binary and ternary calcium apatite phosphates are not mere additions of the end-member structures, but that structural adjustments must occur to accommodate mixed-anion columns. Table 2 depicts the distance between anion occupants of adjacent planes, and illustrates which adjacent neighbors are allowed with mixtures of the end-member structures. 

This element occurs abundantly in the bones of animals, in combination with oxygen and metals, as phosphate of lime, phosphate of magnesia, ( . It is also an ingredient in some unknown form of combination, of vegetable and animal fibrine and albumen, and is constantly present in the urine and excrements. In the mineral kingdom it occurs as phosphate of lime (apatite), phosphate of alumina (wavellite), phosphates of lead, copper, c. 

Some other supports present the same behavior as for instance, as displayed in Fig. 3, S200 (from DEGUSSA), which is a silica with a 316 m g BET surface area and a 704 nm mean pore diameter, or an apatitic phosphate (86 m g and 8.3 nm). 

S.2.3 Aluminum and Iron Phosphates - A total P2O5 analysis of a potential ore is not a dependable criterion for evaluation of a phosphate deposit. With the weathering of apatitic phosphates and associated minerals, a suite of other secondary phosphate minerals may form (Table 5.7). These minerals are most com--monly-aluminurn and.irorhConteining phosphates. These minerals cannot be processed by the methods used to beneficiate apatitic calcium phosphates. Aluminum and iron phosphate minerals may form in both sedimentary and igneous deposits. 

The commercial wet process consists essentially of grinding the apatite phosphate rock, reacting it with acid, and then separating the insoluble calcium sulphate by filtration (5.7). In practice, the... 

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