Single crystals of tetracalcium iridium hexaoxide, Ca(4)IrO(6), tricalcium magnesium iridium hexaoxide, Ca(3)MgIrO(6), and tricalcium zinc iridium hexaoxide, Ca(3)ZnIrO(6), were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The three compounds are isostructural and adopt the K(4)CdCl(6) structure type, comprised of chains of altern...