Cu3B7O13I is cubic, space group F̅43c, with a 12.0203(7) Å; d.(calcd.) = 4.608 for Z = 8. Final R = 0.014 for 110 unique reflections. At. parameters are given. This new boracite has been prepared by high-pressure synthesis; its structure is comparable with that of other cubic boracites. No structural phase transition could be observed between 15 and 1265 K

Cr3B7O13I is cubic, space group F.hivin.43c, with a 12.214(1) .ANG.; dc = 4.130 for Z = 8. Final R = 0.023 for 109 reflections. At. coordinates are given. Shortest interat. distances are Cr-O 2.075(2), Cr-I 3.0520(2), O-B 1.439(3), and O-O 2.393(3) .ANG.. The deviation from planarity of the O-atom environment around the metal atom is compared with those of other cubic boracites

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Dielectric constant, spontaneous polarization and birefringence have been measured between 10 K to 290 K on single domain samples of Cu3B-f)13Br.