Clinoenstatite: High-Low Inversion

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Science  21 May 1965:
Vol. 148, Issue 3673, pp. 1090-1091
DOI: 10.1126/science.148.3673.1090


Clinoenstatite undergoes a metastable displacive inversion at 995°C. The new phase can be indexed (from x-ray powder pattern) on a triclinic cell with dimensions a = 10.00 Å; b = 8.934 Å; c = 5.170 Å; alpha = 88.27°; beta = 70.03°; gamma = 91.09°. The new phase persists from 995° to 1010°C at the composition MgSiO3. For a solid solution (15 percent by weight) of diopside in clinoenstatite, the new phase persists from 995° to at least 1400°C and does not invert in periods of several hours to protoenstatite, the phase previously thought to be the stable form in this region.