Garnets description

See p. 500 of ref. 24 for a description of Ihe garnet structure which is also adopted by inany. synthetic and non-silicaie coniponnds these have been much stndied recently becan.se of their important optical and magnetic properties, e.g. ferrimagnetic vitriuni iron garnet (YIG), y> Fe (Al" b4),. 

Figure 4.11 Monte-Carlo simulation (100 trials) of error propagation for La/Yb fractionation in residual melts by clinopyroxene-garnet removal from a basaltic parent magma (see text for parameter description and distributions used). Top mineral-liquid partition coefficients for La and Yb. Bottom variations of the La/Yb ratio as a function of the fraction F of residual melt.

From the beginning it was noted that the structure was dominated by large columnar elements of the garnet structure type The doubt has been about the remaining parts (between the garnet columns). The garnet structure itself is rather complicated it has only recently been given a satisfactory description in terms of articulated, cation-centred polyhedra The vesuvianite structure is even more complex. 

Description of garnet morphology and zoning from each domain... 

Althoiigh, experimentally, SrTiOj is not ferroelectric even at low temperatures, it is very close to the ferroelectric threshold. The isotopic replacement of oxygen or partial cation substitution reduces quantum fluctuations and makes it ferroelectric. Hence, SrTiOs will serve as a model material to apply the Landau theory to a quantitative description of the displacive phase transition. Similar descriptions of structural phase transitions have been provided for many minerals, including feldspars (e.g.. Carpenter, 1988), garnets (Carpenter and Boffa Ballaran, 2001), quartz (Carpenter et al., 1998), or cristobaUte (Schmahl et al., 1992). 

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