Abstract
A single crystal of a birefringent Cr-bearing majorite, Mg3Mg0.34Si0.34Al0.18Cr0.14)2Si3O12, was synthesized at 20 OPa and 2000 °C using “6-8” type uniaxial split-sphere apparatus. This garnet is tetragonal with the unit-cell parameters a ≈ c and deviates slightly from cubic symmetry. The structure refinements using single-crystal X-ray diffraction intensity data were carried out by assuming three space groups (one cubic and two tetragonal) to determine the most probable symmetry. The most probable space group is I41/a (tetragonal). The Cr ions show a disordered distribution between the two nonequivalent octahedral sites in the I41/a structure.
Received: 1998-5-27
Accepted: 1998-9-7
Published Online: 2015-11-13
Published in Print: 1999-1-1
© 2015 by Walter de Gruyter Berlin/Boston
