What's the half-life of uranium?
Uranium
In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%).[4] Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,[5] making them useful in dating the age of the Earth.
Nuclear isomer
Holmium's nuclear isomer,  has a half-life of 1,200 years, which is nearly the longest half-life of any holmium radionuclide. Only , with a half-life of 4,570 years, is longer.