The crystal structures of loparite-(Ce)

The structures of three compositionally distinct crystals of loparite-(Ce) have been determined by single-crystal X-ray diffractometry using a CCD are a detector. Niobian calcian loparite-(Ce) from the Khibina complex, in Russ ia, is orthorhombic [Pbnm; a 5.5108(14), b 5.5084(14), c 7.7964(20) Angstro m]. Calcian niobian loparite-(Ce) from the Lovozero complex, also in Russia , is tetragonal [14/mcm; a 5.5022(11), c 7.7967(16) Angstrom]. Strontian ca lcian loparite-(Ce) from the Bearpaw Mountains, in Montana, is tetragonal [ 14/mcm; a 5.5076(17), c 7.7767(24) Angstrom]. None of these samples show an y evidence of cation order at the A or B site. All examples of loparite-(Ce ) have the general formula (Na,Ce,Ca)(2)(Ti,Nb)(2)O-6, These structural and compositional data indicate that loparite requires redefinition as a miner al species.