Zirconolite, a complex oxide with an idealized formula (Ca,REE)Zr(Ti,Fe,Nb)2O7, is an accessory mineral of Nb ores from alkali pegmatites and carbonatites of the Vishnevogorsk alkaline complex (South Urals, Russia). Tabular grains of zirconolite (3-25 μm across) occur in assemblages with pyrochlore, zircon, titanite, ilmenite, and calcite. The chemical composition of zirconolite (wt. %, Fe is considered as Fe2+) is as follows: CaO 8.5-9.3; Y2O3 0.0-1.3; REE2O3 10.0-12.2; ZrO2 28.8-29.6; TiO2 24.4-25.5; Nb2O5 13.1-13.4; Ta2O5 1.1-2.0; FeO 7.3-8.6; total 97.9-99.5. The average chemical composition of the mineral is close to formula CaREEZr2Ti2NbFe2+O14.

Figures 4. Table 2. References 8.

Key words: zirconolite, alkali pegmatites, Vishnevye Mountains, South Urals.

V.A. Popov, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia; popov@mineralogy.ru

V.I. Popova, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia;

I.A. Blinov, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia;

V.A. Kotlyarov, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia

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