The crystal structure of cryolithionite, originally solved by Menzer, has been refined by least squares treatment of single-crystal data. Cryolithionite has the garnet structure with lattice constant 12.122 ± 0.002 Å. The ionic distribution as originally given by Menzer, namely {Na3} [Al2 (Li3)F12, is confirmed. Cryolithionite is the only known garnet in which the tetrahedral cation-anion (Li+ – F) distance, 1.846 ± 0.003 Å, is longer than the octahedral cation-anion (Al3+-F-) distance, 1.807 ± 0.003 Å. The Na+-F distances are 2.351 ± 0.003 and 2.544 ± 0.003Å.

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