One is the Carbon-14 system used for dating fragments of once-living organisms.
It's never used for non-organic samples, and almost never even attempted if the sample is thought to be much older than about 50,000 years.
Most people, even the experts in the field, forget the assumptions on which radiometric dating is based.
Radioactive Dating There are basically two different kinds of radioactive dating methods.
The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.