Bull. nat. Hist. Mus. Lond. (Geol.)52(1); 1-24 
Issued 27 June 1996 
Zirconolite: a review of localities worldwide, and 
a compilation of its chemical compositions 
C.T. WILLIAMS 
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, U. 
R. GIERE 
THE NATURA 
27 JUN 1996 
PRESENTED 
Mineralogisch-Petrographisches Institut der Universitat, Bernoullianum, CH-4056, Basel, Switzerland| AEONTOLOGY LIBRARY 
Cals 
Synopsis. A compilation of the chemical data and brief review of the mineral zirconolite, essentially CaZrT1,0,, is 
presented. A total of 321 chemical analyses, 169 previously unpublished, from 39 of the 46 known terrestrial localities, 
and covering 10 rock types are tabulated. A brief description of the minerals associated with zirconolite is outlined for 
each locality. Data from all zirconolite-bearing lunar rocks have also been compiled. The recently published nomenclature 
scheme for zirconolite is employed throughout. 
INTRODUCTION 
Zirconolite, although a relatively rare accessory mineral, 1s 
found in a wide range of rock types and _ geological 
environments. To date, zirconolite has been reported from 46 
terrestrial localities and from 13 lunar samples: it has not been 
reported in meteorites. The chemical composition of natural 
zirconolite can vary extensively, with the main substitutions 
involving rare earth elements, actinide elements, niobium and 
iron. Synthetic zirconolite is a major component in SY NROC, a 
synthetic polyphase titanate ceramic designed to immobilise 
high-level radioactive waste. 
In this paper, we compile and tabulate all reported chemical 
data for natural zirconolites, including new, and previously 
unpublished analyses; we group zirconolites into specific rock 
types or paragenetic types, and denote those samples that are 
stored in the collections of the Mineralogy Department, The 
Natural History Museum, London. 
NOMENCLATURE 
In the literature, several minerals with stoichiometries close to 
CaZrTi,O,, but with different crystal structures, have been 
reported and this has led to confusion in the nomenclature of 
these minerals. The compound CaZrTi,O, can exist as three 
superstructures with monoclinic, orthorhombic and trigonal 
symmetries (Rossell, 1980), each being a polytype (White, 1984), 
subsequently redefined as polytypoids (Bayliss e7 al., 1989). 
However, the original type material, polymignite (Berzelius, 
1824), zirkelite (Hussak & Prior, 1895) and zirconolite (Borodin 
et al., 1956) are metamict and their structures cannot be 
unambiguously defined. Further problems in identification and 
characterisation have arisen, in part because the frequent 
occurrence of actinide elements in the structure may render the 
mineral partially or totally metamict, and in part because the 
often small grain size does not allow for routine crystallographic 
techniques to be employed. These nomenclature problems have 
been addressed by Nickel & Mandarino (1987) and most 
© The Natural History Museum, 1996 
recently by Bayliss et al. (1989), who summarized the 
crystallographic and chemical characteristics of these minerals, 
detailed their historical documentation, and rationalized their 
nomenclature. 
Under the Bayliss et a/. (1989) IMA-approved nomenclature 
scheme, zirconolite is the non-crystalline (metamict) mineral, or 
the mineral with undetermined polytypoid of CaZrTi,0,; 
zirconolite-3O is the three-layered orthorhombic polytypoid of 
CaZrTi,O,; zirconolite-3T is the three layered trigonal 
polytypoid of CaZrTi,O,; zirconolite-2M is the two-layered 
monoclinic polytypoid, or aristotype (White, 1984) of 
CaZrTi,O,; zirconolite is polymignite (metamict), and zirkelite 
is the cubic mineral with formula (Ti,Ca,Zr)O, ,. Smith & 
Lumpkin (1993) have subsequently described two additional 
polytypes which appear to be supercells of the zirconolite-2M 
and 3T structures (zirconolite-4M and -6T, respectively). 
CHEMICAL COMPOSITION 
Zirconolite has five cation-acceptor sites, these being Ca in 
8-coordination, Zr in 7-coordination, and three distinct Ti sites: 
Ti(I) and Ti(IIl) are both 6-coordinate, and Ti(II) is 
5-coordinate (Gatehouse et al., 1981; Mazzi & Munno, 1983). In 
natural (and synthetic) zirconolites, a wide range of cation 
substitutions can occur (e.g. Ringwood, 1985), ranging in ionic 
size from 0.051nm (Ti**) to 0.112nm (Ca?*) — ionic radii data 
from Shannon (1976) — and charge from 2+ (Mg) to 6+ (W). 
Predominant substitutions are: the rare earth elements including 
Y (REE) and actinide (ACT) elements for Ca; Hf for Zr; and 
Nb, Fe, Ta, Mg and W for Ti. In natural zirconolites the 
chemical variation is extensive; of the major components, CaO 
ranges from 1.83 to 16.54%, ZrO, from 22.82 to 44.18%, and 
TiO, from 13.56 to 44.91% (Table 1). Up to 79% of the Ca site 
can be replaced by other cations (e.g. analyses A4, L11, Table 3), 
and up to 65% of the Ti site (analysis C69, Table 3). 
TIT er 
| HISTORY MUSEUM 
