High-pressure synthesis and properties of magnesiocarpholite,MgAl2[Si2O6] (OH)4 |
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| Authors: | Christian Chopin Bruno Goffé |
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| Institution: | (1) Institut für Mineralogie, Ruhr-Universität, D-4630 Bochum l, Federal Republic of Germany;(2) Laboratoire de Géologie (E.R. 224), Ecole normale supérieure, 46 rue d'Ulm, F-75005 Paris, France |
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| Abstract: | Magnesiocarpholite has been synthesized on its own composition between 15 and 25 kb water pressure and 415°–600° C. Best conditions are 25 kb-550° C, starting from a mixture of oxides and synthetic cordierite. Within the MgO-Al2O3-SiO2-H2O system, possible substitutions appear to be very limited in magnesiocarpholite. Cell-parameters are a=13.706(3), b= 20.075(3), c=5.107(l) Å, space group Ccca. The larger cell, as compared with the most magnesian natural carpholites, is tentatively ascribed to structural disorder. Preliminary stability data confirm the low-temperature character of this mineral which is shown to be a high-pressure equivalent of sudoite+quartz. |
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