APATITE-RELATED MINERALS

The minerals with apatite-like structures are dealt with in detail elsewhere in this volume and will not be considered here, except to list the relevant minerals (for completeness) in Table 12. 

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Besides apatite, luminescence of Mn + has been found in other phosphate related minerals, such as triphte (Ajo et al. 1997). It was proposed that the lattice distortion is smaller for the substituting Mn + ion than for the structural which explains the occurrence of Mn + in several mineral phosphates, while the oxidizing state V is unusual for Mn in aqueous solutions. 

Hahn TJ (1989) Aluminum-related disorders of bone and mineral metabolism. In Bone and Mineral Research. Vol. 6. Peck WA (ed) Elsevier, New York Hounslow AW, Chao GY (1968) Monoclinic chlorapatite from Ontario. Can Mineral 10 252-259 Hughes JM, Cameron M, Crowley KD (1989) Stmctural variations in natural F, OH and Cl apatites. Am Mineral 74 870-876... 

Hydroxyapatite, Ca2Q(PO (OH)2, may be regarded as the parent member of a whole series of stmcturaHy related calcium phosphates that can be represented by the formula M2q(ZO X2, where M is a metal or H O" Z is P, As, Si, Ga, S, or Cr and X is OH, F, Cl, Br, 1/2 CO, etc. The apatite compounds all exhibit the same type of hexagonal crystal stmcture. Included are a series of naturally occurring minerals, synthetic salts, and precipitated hydroxyapatites. Highly substituted apatites such as FrancoHte, Ca2Q(PO (C02) (F,0H)2, are the principal component of phosphate rock used for the production of both wet-process and furnace-process phosphoric acid. 

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

Relatively recently, AIS Sommer GmbH of Germany delivered a laser-induced fluorescence (LIP) analyzer for quality control in minerals and mineral processing (Broicher 2000). The LIP analyzer includes two light detector systems with three photomultipliers each, which evaluate three spectral bands in two time windows each. It was done in the Kiruna phosphorous iron ore mine, Sweden. The limitation of LIP analysis is that its accuracy depends on the complexity of the composition of the ore and the concentration and fluorescence properties of the critical minerals in relation to all the other minerals present. The phosphorous iron ore in Kiruna is ideal for LIP analyzes, because its iron minerals are practically non-luminescent, while magmatic apatite is strongly fluorescent with intensive emissions of Ce and Eu ". ... 

Calcium in Plant and Animal Nutrition. Calcium is essential to plant and animal life and is present in adequate amounts in many soils (78). The outer green leaves of cabbages and certain other leafy vegetables contain much more calicum than the inner white ones (79, 80, 81). Large amounts of it are present in the human body. The composition of bone suggests that it must be closely related to the apatite series of minerals, which have the formula nCa3(PO.t )2-CaC03, in which n has a value... 

Crystallinity is a metric related to mineral maturity and is a measure of mineral crystallite size, mineral maturity, and the amount of substitution into the apatitic lattice. Crystallinity increases when crystals are larger and more perfect (i.e. less substitution). It is directly proportional to the inverse width of the 002 reflection (c-axis reflection) in the powder x-ray diffraction pattern of bone mineral. Several features in the infrared spectra of bone correlate with mineral crystallinity, most of which are components of the phosphate Vi,V3 envelope [8]. Any of these correlations should be usable in the Raman spectrum provided there are no other overlapping Raman peaks. However, there has been less emphasis on crystallinity in the bone Raman literature and only the inverse width of the phosphate Vi band has been used as a measure of crystallinity [9-12]. 

As discussed in Chapters 5 and 7, the use of lime to precipitate calcium arsenates is a common method for removing inorganic As(V) from water or flue gases. Calcium arsenates were also once extensively used in pesticides (Chapter 5). The compositions of some calcium arsenates, such as johnbaumite (Ca5(As04)3(0H) Table 2.5), resemble the very common phosphate mineral, apatite (Ca5(P04)3(F,Cl,0H)), where arsenate replaces phosphate. Some lead arsenates, such as mimetite (Pb5(As04)3Cl Table 2.5), also have crystalline structures that are related to apatite. Mimetite may occur in oxidized lead-rich hydrothermal deposits. 

The listed chemical formulae are ideal and most of these minerals contain trace and minor elements which undoubtedly affect the CL. Several of these minerals have polymorphic or compositional varieties which also may, or do, show CL (e.g. the silica polymorphs quartz, cristobalite, tridymite phosphate compositional varieties apatite, whitlockite, farringtonite, buchwaldite carbonate compositional varieties calcite, dolomite, magnesite). Glass and maskelynite (shock modified feldspar), although not strictly minerals, are relatively common. Below are described the CL observations for the most common phases including enstatite, feldspar and forsterite and they are related to their use for interpreting the mineralogy of meteorites. The observations for the other minerals are sporadic and many details have yet to be studied. 

Vukadinovic D. and Edgar A. D. (1993) Phase relations in the phlogopite-apatite system at 20kbar implications for the role of fluorine in mantle melting. Contrib. Mineral. Petrol. 114, 247 -254. 

Accessory minerals commonly contain high concentrations of radioactive elements, and are a common target of radiogenic isotope measurements. Specific elements include uranium (zircon, apatite, titanite, monazite, xenotime, allanite) and thorium (monazite and allanite). Each accessory mineral is stabilized in a rock via a single element or suite of related elements, specifically phosphorous (apatite), REE (allanite, monazite, xenotime), zirconium (zircon), and titanium (titanite). Trace elements also occur in the major minerals (particularly phosphorous, zirconium, and titanium), so accessory minerals participate directly in major mineral reactions (Pyle and Spear, 1999, 2000, 2003 Ferry, 2000 Pyle et al, 2001 ... 

Reiterating, the phosphatic mineral of such phosphorites is essentially francolite, a carbonate fluorapatite of somewhat variable composition (McConnell, 1971 Rooney and Kerr, 1967). Although not proven to be contained within the apatitic phase through isomorphic substitution, some of the continental phosphorites are of considerable interest because of accumulations of uranium, thorium, yttrium, rare earths, scandium, and vanadium therein. These rarer components are thought to be related to diagenetic processes, in which case they were extracted from sea water during the early formative histories of the phosphorites. 

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