Some nuclides are inherently unstable. But the whole point I wanted to do this is to show you that it's not some crazy voodoo here. This shows we should not trust radiometric dating. In nearly all of the dating methods, except potassium-argon and the associated argon-argon method, there is always some amount of the daughter product already in the rock when it cools. However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits. Hidden categories: Because of uranium's long half-lives, these halos take at least several hundred million years to form.
Each decays through a series of relatively short-lived radioactive elements that each decay to a lighter element, finally ending up at lead.
Exposure to sunlight or heat releases these charges, effectively "bleaching" the sample and resetting the clock to zero. The uranium content of the material can then be calculated from the number of tracks and the neutron flux. Some Naturally Occurring Radioactive Isotopes and their half-lives.