The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists
Online ISSN : 1883-0765
Print ISSN : 0021-4825
ISSN-L : 0021-4825
Some observations on the synthetic gehlenites
Takashi Yoshioka
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1969 Volume 61 Issue 3 Pages 106-111

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Abstract

Observations were made on the synthetic gehlenites obtained by heating the glasses of 2CaO•Al2O3•SiO2 (gehlenite)-CaO•2Al2O3 and 2CaO•Al2O3•SiO2 (gehlenite)-CaO•3SiO2 compositions.
It was observed that the specimens heated under 1100°C-6 hours condition were composed only of gehlenite single phase up to 16.6% CaO.2Al2O3 content in the glass composition. The lattice constants a0 and c0 of the gehlenite crystallized from the glasses of 2CaO•Al2O3•SiO2-CaO•2Al2O3 system were greater than those of pure gehlenite. The more than CaO•2Al2O3 component in the glass composition, the greater was the a0 of gehlenite crystallized therefrom. By prolonged time of heating the a0 of the gehlenite decreased. At higher temperatures it became smaller near to that of pure gehlenite and separated CaO•2Al2O3 crystal.
In the heating experiment of the glasses of 2CaO•Al2O3•SiO2 (gehlenite)-CaO•3SiO2 composition, gehlenite single phase was obtained up to 11.2% CaO•3SiO2 composition.
Refractive indices and lattice constants a0, c0 of the formed gehlenite decreased continuously with increasing amount of CaO•3SiO2 component up to 11.2% CaO.3SiO2 composition. Lattice constants of the gehlenite became greater and near to those of pure gehlenite when crystallized at higher temperatures.
As a result, it was confirmed that gehlenite when crystallized at lower temperatures from the glasses of 2CaO•Al2O3•SiO2-CaO•2Al2O3 and 2CaO•Al2O3•SiO2-CaO•3SiO2 compositions could have unstably more aluminous or more siliceous composition than that of pure gehlenite Ca2Al2SiO7.

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