Sources of curium
Curium is made synthetically. 242Cm and 244Cm are available in multigram quantities, but 248Cm has been produced only in milligram amounts.
Minute amounts of curium probably exist in natural deposits of uranium, as a result of a sequence of neutron captures and beta decays sustained by the very low flux of neutrons naturally present in uranium ores. There is no evidence, however, to suggest that natural curium exists today. It may, however, have existed long ago. The most stable isotope of curium, 247Cm, has a half-life of 16 million years. Compared to the Earth’s age, this is relatively short. Consequently, if any primordial curium did exist, it would have disappeared millions of years ago.