Apatite group

Ninety five percent of the phosphorus on Earth belongs to the minerals of the apatite group. Apatites are inorganic constituents of bones and teeth of vertebrate and man, as well as a basis of many pathologic sohd formations. Minerals of the apatite group are the main raw materials in the production of phosphorus fertilizers, fodder and technical phosphates, elementary phosphorus, and phosphor-organic compounds. The mineral is sometimes substantially enriched in rare-earth elements (REE) making their extraction possible (Altshuller 1980). 

Pyromorphite belongs to the apatite group. This group is divided into two series, the apatite series and pyromorphite series. These minerals are isostruc-tural, however the unit cell volume of pyromorphite is about one-fifth larger... 

The apatite group minerals are the most abundant phosphorus-bearing minerals on Earth, typically as accessory minerals in basic to acidic igneous rocks, pegmatites, hydrothermal veins and cavities, carbonates, contact and regionally metamorphosed rocks, and sedimentary rocks (Deer et al. 1996). The principal members of the apatite group include fluoroapa-tite (Ca5(P04)3F), chloroapatite (Ca5(P04)3Cl), hydroxyapatite, and carbonate apatite (Ca5(P04, C03)3(F,0H)) (Deer et al. 1996). 

Of the four prominent pure end-member phosphate species of the apatite group only dahllite (space group C63/m) is a common biomineral28. This carbonate apatite is a distinct variety of apatite rather than a mixture of CaC03 and hydroxyapatite. Expressed as oxides, the mineral content of bovine cortical bone (dry fat-free material) has the following chemical composition112 ... 

Dunn, P.J., Pecor, D.R. and Newberry, N. (1980) Johnbaumite, a new member of the apatite group from Franklin, New Jersey. American Mineralogist, 65, 1143-45. 

The most common and widely distributed phosphate minerals are the apatite group, with the general formula Ca10(PO4)6(X)2. The apatite is designated as fluorapatite, hydroxyapatite, or chlorapatite, when X = F, OH, or Cl, respectively. The most abundant sedimentary apatite is carbonate fluorapatite (ffancolite). Relative to pure fluorapatite, francolite is characterized by the substitution of Na and Mg for Ca and of carbonate and fluoride for phosphate. An empirical formula for francolite... 

Na-containing member of apatite group K-containing member of apatite group Mg3(P04)2 8 H2O (monocl.)... 

Chakhmouradian, A.R. and Medici, L. (2006) Clinohydroxylapatite a new apatite-group mineral from northwestern Ontario (Canada), and new data on the extent of Na-S substitution in natural apatite. Ear. J. Mineral, 18 (1), 105-112. 

Ores—Part I Electrochemical Properties of Some Minerals of the Apatite Group Pan II Electrochemical Phenomeon at [be Caicite/Aquoons Interface, Trans. SME/AIME, 258, 168 (1975). 

The term apatite sensu stricto defines three unique minerals, fluorapatite [Ca5(P04)3F], chlorapatite [Ca5(P04)3Cl], and hydroxylapatite [Ca5(P04)3(0H)], all with Z = 2. As shown by numerous authors, most recently Hughes et al. (1989), the atomic arrangements of the three apatite phases differ principally in the positions of the occupants of the 0,0,z anion positions, i.e., fluorine, chlorine, and hydroxyl for the three end-members, respectively. Below we compare the component polyhedra of the three phases and use this comparison as a basis for subsequent discussion of other apatite group phases. Portions of the comparison are taken from Hughes et al. (1989), which also cites previous works that provide a rich history of research on mineralogical apatite. Table 1 provides the atomic parameters for well-characterized samples of fluorapatite, hydroxylapatite, and chlorapatite (Hughes et al. 1989). 

Compositions of the Apatite-Group Minerals Substitution Mechanisms and Controlling Factors... 

The apatite-group minerals of the general formula, Mio(Z04)6X2 (M = Ca, Sr, Pb, Na..., Z = P, As, Si, V..., and X = F, OH, Cl...), are remarkably tolerant to structural distortion and chemical substitution, and consequently are extremely diverse in composition (e.g., Kreidler and Hummel 1970 McConnell 1973 Roy et al. 1978 Elliott 1994). Of particular interest is that a number of important geological, environmental/paleoenvironmental, and technological applications of the apatite-group minerals are directly linked to their chemical compositions. It is therefore fundamentally important to understand the substitution mechanisms and other intrinsic and external factors that control the compositional variation in apatites. 

This chapter outlines the compositional variations of the apatite-group minerals, with emphasis on the chemical substitutions that appear to be responsible for these variations. We purposely include data from the large number of synthetic apatites, which may or may not... 

A large number of divalent cations (Si, Pb, Ba, Mn, etc.) have been reported to substitute for Ca in the apatite-group minerals. Similarly, many monovalent (e g., Na, ... 

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