The crystal structure of a noncubic garnet of composition And94Gr5Spess1 was refined from single-crystal X-ray diffraction intensities to Rw = 2.4% for 3145 observations unique under Laue group 1. Although the unit cell is metrically cubic, with a = 12.048(1) Å the space group for this optically anisotropic garnet is found to be I1, a subgroup of Ia3d. Partial long-range ordering of Fe3+ and Al over the eight symmetrically unique octahedral sites of the I1 structure is found to be significant and is cited as a possible origin for the observed optical anisotropy.

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