Pyrope

Kapgranat, m. Cape ruby (pyrope). kapillar, a. capillary. 

The importance of the size of the solute relative to that of the solvent mentioned above is evident also from experimental determinations of the extent of solid solubility in complex oxides and from theoretical evaluations of the enthalpy of solution of large ranges of solutes in a given solvent (e.g. a mineral). The enthalpy of solution for mono-, di- and trivalent trace elements in pyrope and similar systems shows an approximately parabolic variation with ionic radius [44], For the pure mineral, the calculated solution energies always show a minimum at a radius close to that of the host cation. 

Broadband LIBS spectra for three garnet types - the Mg-AI pyrope type, the Ca-AI grossular type, and the Mn-AI spessartine type are shown in Figure 1. 

Fig.1. Example broadband LIBS spectra for a pyrope, grossular, and spessartine garnet. The clear differences observed in the broadband spectra reflect the chemical differences in the composition of the three garnets.

Classification Assignment Fig. 4. Confusion matrix for the HDPCA analysis of the four pyrope garnets. The nth row and column correspond to the nth pyrope type truth and HDPCS statistical assignment, respectively. 

Because of the importance of garnet in upper-mantle parageneses, the compressibility of this phase has been the subject of many experimental studies. Ha-zen and Finger (1978), studying the compressibility of pyrope, observed that the... 

Leitner et al. (1980) showed that the bulk moduli of terms of pyrope-almandine-grossular and andradite-grossular mixtures vary with chemical composition in a perfectly linear fashion (within the range of experimental incertitude). This behavior is also implicit in the generalization of Anderson (1972). 

Table 5.24 lists selected data concerning entropy and isobaric heat capacity, covering andradite, grossular, pyrope, and almandine terms, compared with results of calculations based on the Kieffer model (Ottonello et al., 1996). 

Figure 5.16A shows, for example, how calculated Cp values for pyrope compare with low-T calorimetric measurements of Haselton and Westrum (1980). Adopting the initial guess value of (115.7 cm see table 5.25) leads to an entropy estimate at =... 

Figure 5.16 Heat capacity of pyrope at constant P, as determined from the Kieffer vibrational model, compared with low-P (upper part of figure) and high-P (lower part of figure) experimental evidences. From Ottonello et al. (1996). Reprinted with permission of The Mineralogical Society of America.

Table 10.3 Defect equilibria affecting REE solubility in pyrope and their effects in bulk garnet/melt REE distribution (Morlotti and Ottonello, 1982)...

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