Garnets composition

Consultants Ltd., United Kingdom). The analyses were performed on pyroxene and garnet crystals of exoskarn facies. Microprobe data obtained from pyroxene shows a wide composition variation that fluctuates between 53-80 wt.% Di, 20-47 wt.% Hd, and minor amounts of Jo (0.05-0.36 wt.%). Furthermore, mineral garnet composition ranges between 68-99 wt.% Grs, 0-20 wt.% Ad, 0-8 wt.% Aim, and 0-0.75 wt.% Prp. These significant changes are mainly linked to the variations in the magmatic fluid composition of the system, where Fe, Mg, Al, and Si contents show an erratic behaviour, whereas Ca values remain constant. 

Although the garnet compositions used in memories contain rare earths, the total rare earth use in magnetic films is not sufficient to make much impact on the rare earth market. The use of gadolinium oxide in substrate crystals is another matter. It has been estimated that by 1990 the annual use of Gd203 for GGG substrates will reach 40 metric tons, about twice the present rate (21). 

Perhaps more than in most other examples that can be cited of materials exploitation, designing a ferrite for a particular microwave application is a compromise a desired value for a particular parameter is generally achieved at the expense of the optimum values of other parameters. Nevertheless, a select number of spinel and garnet compositions have become favoured for microwave applications. 

Restricted to Matsoku. Orthopyroxene and clinopyroxene rich rocks with widely variable olivine and garnet compositions, often with ilmenite and phlogopite (the IRPS suite see type VIII). Bulk compositions Fe and Ti rich. Form magmatic intrusions (<16 cm thick) into type I rocks which become metasomatized. 

Figure 47 Garnet compositions for eclogites from Siberia, South Africa, and Koidu (Sierra Leone) compared to low-L Kaapvaal peridotites, in terms of their pyrope, grossular, and almandine calculated end-members (sources Sobolev, 1974 Hatton and Gurney, 1987 Mazonne and Haggerty, 1989 Taylor and Neal, 1989 Jacob et al, 1994 Hills and Haggerty, 1989 Viljoen et al., 1996 Pyle and Haggerty, 1998 and Barth et al, 2001).

Figure 4 Plot of garnet composition versus radius for garnet growth between 500 °C and 577 °C at 6 kbar. Assemblage and chemical system are the same as in Figure 3. Dotted lines show trace of equilibrium compositions, which result from phase equilibrium effects. Solid lines show fractional crystallization model. Similarity of curves for all components (not just Mn) indicates that phase equilibria strongly control garnet chemical compositional changes, but significant differences between curves, especially for Mn, indicate that fractional crystallization is also important (source Spear, 1993).

Tracy R. J., Robinson P., and Thompson A. B. (1976) Garnet composition and zoning in the determination of temperature and pressure of metamorphism, central Massachusetts. Am. Mineral. 61, 762-775. 

Table 14.1 A typical garnet composition. FeO = total iron reported as FeO. Sevigny and Ghent (1989), sample S129.

Answer I think so—there are some technical ferrites made by spray-drying. We tried to flame-spray various garnet compositions from alcohol-nitrate solutions but it does not work very well. This was in connection with the making of films on glass substrates. 

Phosphorescence and Fluorescence Many ceramics phosphoresce and fluoresce. These ceramics find applications in fluorescent lights, oscilloscope screens, television screens, electroluminescent lamps, photocopy lamps, and lasers. Lasers include tungstates, fluorides, molybdates, and garnet compositions doped with chromium, neodymium, europium, erbium, praseodymium, and so on. Ceramic phosphor is Ca5(P04)3(Cl,F) or Sr5(P04)3(Cl,F) doped with Sb and Mn. Figure 1.9 shows some configurations of fluorescent lights. 

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