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)O_2−x.