Letter | Published:

Cube-Edges of Uraninites as a Criterion of Age

Naturevolume 168page380 (1951) | Download Citation



I HAVE suggested that there is a progressive reduction in the size of the unit cell of uraninite-thorianites with time1. The ionic radius of Pb4+ is appreciably smaller than those of U4+ and Th4+. The decay of the parent element causes its substitution by radiogenic lead within the crystal lattice; because of the differences in sizes of the ions, a shrinkage results. It is therefore likely that this factor can be utilized for indicating the relative ages of uraninites after these have been subjected to an X-ray powder examination. No great accuracy can be envisaged, but such a method would be more accessible to geologists than the highly refined mass-spectrographic one, which can be practised in very few laboratories in the world.

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    Wasserstein, B., Proc. Geol. Soc. S. Afr. (in the press).

  2. 2

    Arnott, R. J., Amer. Mineral., 35, 386 (1950).

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    Bradley, A. J., and Jay, A. H., Proc. Phys. Soc., 44, 563 (1932).

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    Wasserstein, B., Amer. Mineral., 36, 102 (1951).

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    Ingerson, E., Amer. Mineral., 23, 269 (1938).

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    Holmes, A., Trans. Edin. Geol. Soc., 14, 176 (1948).

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    Holmes, A., Amer. J. Sci., 248, 81 (1950).

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  1. Geological Survey, P.O. Box 401, Pretoria



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