References for Selected Phosphate Minerals

A tabulation of data and references for selected phosphate minerals (on the following 17 pages) 

Department of Geology University of Maryland College Park, Maryland 20742 

Fluorapatite is by far the most common member of apatite family found in igneous rocks. However, most natural fluorapatite contains some chlorine and hydroxyl as well, and these constituents can attain high concentrations in some cases. The other halogens, bromine and iodine, also occur in apatite, but their concentrations are much lower than chlorine and fluorine. Many cations commonly substitute for calcium and phosphorus in apatite, however, they rarely reach concentrations that warrant the definition of a separate mineral species. 

Apatite can be described by the general formula A5(X04)3Z (following Sommerauer and Katz-Lehnert 1985). The A-site accommodates large cations (e.g., Ca , Sr, Pb, Ba, Mg, Mn, Fe, REE, Eu, Cd, Na ) (Pan and Fleet, Ch. 2 in this volume), and comprises two sites that exhibit Vll-fold (Ca2) and IX-fold (Cal) coordination (Hughes and Rakovan, Ch. 1 in this volume). The X-site, occupied primarily by P (as PO4 ) exhibits IV-fold coordination and can accommodate other small highly charged cations (e.g., well as OH.  

As part of this work we have compiled chemical data from the literature on apatite chemistry. In that compilation we consider analyses of apatite from the literature to be of unaltered species, unless the authors specifically state otherwise. In addition, only a limited number of studies (Coulson et al. 2001, Fournelle et al. 1996, Loferski and Ayuso 1995, Meurer and Boudreau 1996, Parry et al. 1978, Piccoli and Candela 1994, Smith 1999) take into consideration the petrographic association of apatite, even though it has been suggested that apatite embedded in hydrous phases can experience retrograde exchange with their hosts, and may therefore have compositions different from apatite grains surrounded by nominally anhydrous phases. For example, apatite within biotite has been found to contain elevated F relative to apatite included within anhydrous phases (e.g., Loferski and Ayuso 1995). 

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