1. Heamanite-(Ce), (K0.5Ce0.5)TiO3, a new perovskite supergroup mineral found in diamond from Gahcho Kué, Canada.
- Author
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Anzolini, Chiara, Siva-Jothy, William K., Locock, Andrew J., Nestola, Fabrizio, Balić-Žunić, Tonči, Alvaro, Matteo, Chinn, Ingrid L., Stachel, Thomas, and Graham Pearson, D.
- Subjects
MINERALS ,PEROVSKITE ,DIAMONDS ,RADIOACTIVE dating ,ELECTRON probe microanalysis ,CRYSTAL structure - Abstract
Heamanite-(Ce) (IMA 2020-001), ideally (K
0.5 Ce0.5 )TiO3 , is a new perovskite-group mineral found as an inclusion in a diamond from the Gahcho Kué mine in the Northwest Territories, Canada. It occurs as brown, translucent single crystals with an average maximum dimension of ~80 μm, associated with rutile and calcite. The luster is adamantine, and the fracture conchoidal. Heamanite-(Ce) is the K-analog of loparite-(Ce), ideally (NaCe)Ti2 O6 . The Mohs hardness is estimated to be 5½ by comparison to loparite-(Ce), and the calculated density is 4.73(1) g/cm3 . Electron microprobe wavelength-dispersive spectrometric analysis (average of 34 points) yielded: CaO 10.70, K2 O 7.38, Na2 O 0.16, Ce2 O3 13.77, La2 O3 8.22, Pr2 O3 0.84, Nd2 O3 1.59, SrO 6.69, BaO 2.96, ThO2 0.36, PbO 0.15, TiO2 45.77, Cr2 O3 0.32, Al2 O3 0.10, Fe2 O3 0.09, Nb2 O5 0.87, UO3 0.01, total 99.98 wt%. The empirical formula, based on 3 O atoms, is: [(K0.268 Na0.009 )Σ0.277 (Ce0.143 La0.086 Pr0.009 Nd0.016 )Σ0.254 (Ca0.326 Sr0.110 Ba0.033 Pb0.001 )Σ0.470 Th0.002 ]Σ1.003 (Ti0.979 Nb0.011 Cr0.007 Al0.003 Fe0.002 )Σ1.002 O3 . The Goldschmidt tolerance factor for this formula is 1.003. Heamanite-(Ce) is cubic, space group Pm3m, with unit-cell parameter a = 3.9129(9) Å, and volume V = 59.91(4) Å3 (Z = 1). The crystal structure was solved using single-crystal X‑ray diffraction data and refined to R1 (F) = 2.61%. Heamanite-(Ce) has the aristotypic perovskite structure and adopts the same structure as isolueshite and tausonite. The six strongest diffraction lines are [dobs in angstroms (I in percentages) (hkl)]: 2.764 (100) (110), 1.954 (41) (200), 1.596 (36) (211), 1.045 (16) (321), 1.236 (13) (310), and 1.382 (10) (220). The Raman spectrum of heamanite-(Ce) shows two broad bands at 560 and 787 cm−1 , with no bands observed above 1000 cm−1 . Heamanite-(Ce) is named after Larry Heaman, a renowned scientist in the field of radiometric dating applied to diamond-bearing kimberlites, mantle-derived eclogites, and lamprophyre dikes. The dominant REE should appear as a Levinson suffix, hence heamanite-(Ce). [ABSTRACT FROM AUTHOR]- Published
- 2022
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