Synthesis and some properties of iron- and vanadium-bearing kyanites, (Al,Fe3+)2SiO5and (Al,V3+)2SiO5 |
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| Authors: | K Langer K R Frentrup |
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| Institution: | (1) Institut für Mineralogie, Ruhr-Universität Bochum, Federal Republic of Germany |
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| Abstract: | Iron- and vanadium-bearing kyanites have been synthesized at 900 and 1100° C/20 kb in a piston-cylinder apparatus using Mn2O3/Mn3O4- and MnO/Mn-mixtures, respectively, as oxygen buffers. Solid solubility on the pseudobinary section Al2SiO5- Fe2SiO5 (-V2SiO5) of the system Al2O3-Fe2O3(V2O3)-SiO2 extends up to 6.5 mole% (14mole %) of the theoretical end member FeSiO5(V2SiO5) at 900°C/20 kb. For bulk compositions with higher Fe2SiO5 (V2SiO5) contents the corundum type phases M2O3(M = Fe3+, V3+) are found to coexist with the Fe3+(V3+)-saturated kyanite solid solution plus quartz. The extent of solid solubility on the join Al2SiO5-Fe2SiO5 at 1 100°C was not found to be significantly higher than at 900° C. Microprobe analyses of iron bearing kyanites gave no significant indication of ternary solid solubility in these mixed crystals. Lattice constants a
0, b
0, c
0, and V0 of the kyanite solid solutions increase with increasing Fe2SiO5- and V2SiO5-contents proportionally to the ionic radii of Fe3+ and V3+, respectively, the triclinic angles  , , remain constant. Iron kyanites are light yellowish-green, vanadium kyanites are light green. Iron kyanites, (Al1.87 Fe
0.13
3+
)SiO5, were obtained as crystals up to 700  m in length. |
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