Clinoenstatite: High-Low Inversion.

Clinoenstatite undergoes a metastable displacive inversion at 995 degrees C. The new phase can be indexed (from x-ray powder pattern) on a triclinic cell with dimensions a = 10.00 A; b = 8.934 A; c = 5.170 A; alpha = 88.27 degrees ; beta = 70.03 degrees ; gamma = 91.09 degrees . The new phase persists from 995 degrees to 1010 degrees C at the composition MgSiO(3). For a solid solution (15 percent by weight) of diopside in clinoenstatite, the new phase persists from 995 degrees to at least 1400 degrees C and does not invert in periods of several hours to protoenstatite, the phase previously thought to be the stable form in this region.