A mechanism for the derivation of U 235 from Cm 247 is considered as a possible source of U 235 enrichment in radiative rare-earth minerals. The presence of Cm 247 in early earth materials is predictable on the basis of synthesis through nuclear reactions and from extrapolations of abundances of lighter nuclides. The chemistry of Cm reflects a geochemical similarity to rare-earth elements and possible incorporation in rare-earth minerals. The amount of enrichment of U that might be expected from Cm 247 decay is calculated for monazite for several geologic ages. Within the limits of the parameters considered, Cm 247 would not provide sufficient U 235 enrichment to be of economic consequence, but its possible existence in early geologic time may be of interest in geochronology studies. Underestimation of Cm 247 abundance may affect significantly the probability for finding interesting variations in U 235 :U 238 ratios.

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