Abstract: The nomenclature of CaZrTi2O7 minerals has become very confused, such that zirconolite, zirkelite and polymignite each have acquired multiple meanings and represent five different crystal structures. To resolve these inconsistencies, the IMA approved resolutions as follows. Zirconolite is the non- crystalline (metamict) mineral or mineral with undetermined polytypoid of CaZrTi2O7. Zirconolite-3O is the three-layered orthorhombic polytypoid of CaZrTi2O7. Zirconolite-3T is the three-layered trigonal polytypoid of CaZrTi2O7. Zirconolite-2M is the two-layered monoclinic polytypoid of CaZrTi2O7. Polymignite (metamict) is discarded as equivalent to zirconolite. Zirkelite is the cubic mineral with formula (Ti,Ca,Zr)O2−x.