gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1989.053.373.07 Mineral Nomenclature: Zirconolite Bayliss Peter Department of Geology and Geophysics, The University of Calgary, Alberta, Canada T2N 1N4 Mazzi Fiorenzo Dipartimento di Scienze della Terra—Sezione di Mineralogia, Petrografia e Geochimica—Via A. Bassi, 4—Pavia, Italy Munno Rosalba Dipartimento di Geofisica e Vulcanologia—Largo San Marcellino, 10—Naples, Italy White Tim J. University of Melbourne, School of Physics, Parkville, Victoria, Australia 3052 12 1989 53 373 565 569 16 12 1988 20 3 1989 Copyright © 1989, The Mineralogical Society 1989 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.

 Keywords zirconolite polymignite zirkelite mineral nomenclature