Pyrope crystal structure

Hazen R. M. and Finger L. W. (1978). Crystal structure and compressibilities of pyrope and grossular to 60 kbar. Amer. Mineral, 63 297-303. 

Meagher E. P. (1975). The crystal structures of pyrope and grossularite at elevated temperatures. Amer. Mineral, 60 218-228. 

Figure 5.5 The crystal structure of garnet (pyrope) projected into a dodecahedron. Note the configuration of the eight-fold coordinated Mg sites (distorted cube) which share edges with [A106] octahedra and [Si04] tetrahedra.

The garnets are a group of minerals having the same crystal structure, but different compositions. Only two of the garnets are commonly red, pyrope, and almandine. The other species in this group occur in all colors except blue. 

Wilkins and Sabine (1973) used IR spectroscopy to determine water contents of kyanite, andalusite, sillimanite, grossular, andradite, pyrope, diopside, olivine, and feldspars. They found low water contents 0.008 wt.% in olivine, 0.02 wt.% in diopside, and 0.009 wt.% in pyrope. Zemann, Beran, and co-workers published a series of papers on IR spectroscopy of both hydrous minerals and NAMs (e.g., Tillmanns and Zemann, 1965 Beran and Zemann, 1971, 1986 Beran, 1971, 1986, 1987 Beran and Gotzinger, 1987 Beran et al., 1993). For the most part, these contributions were focused on the substitutional mechanisms by which hydrogen entered the crystal structure, rather than on the absolute amount of hydrogen in the crystal structure. 

Sawada, H. (1993) The crystal structure of gamets(I) the residual electron density in pyrope, Z. Krist., 203,41-48. 

Armbruster T., Geiger C. A., and Lager G. A. (1992). Single-crystal X-ray structure study of synthetic pyrope ahnandine garnets at 100 and 293 K. Amer. Mineral, 77 512-521. Atkins P. W. (1978). Physical Chemistry. Oxford Oxford University Press. 

Simulated structures for pyrope, ahnandine, spessartme, and grossular were used as the basis for calculations of the energies required to introduce various trace-element defects. In every computational run, one or more defects are introduced into the crystaL e.g., for homo-valent (same-charge) substitution, one divalent cation at the X-site of a perfect garnet lattice is replaced by one trace-element divalent cation. Initial, unrelaxed defect energies were... 

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