Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied.All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.
At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes.
This temperature is what is known as closure temperature and represents the temperature below which the mineral is a closed system to isotopes.
For example, a study of the Amitsoq gneisses from western Greenland used five different radiometric dating methods to examine twelve samples and achieved agreement to within 30 Ma on an age of 3,640 Ma.
Accurate radiometric dating generally requires that the parent has a long enough half-life that it will still be present in significant amounts at the time of measurement (except as described below under "Dating with short-lived extinct radionuclides"), the half-life of the parent is accurately known, and enough of the daughter product is produced to be accurately measured and distinguished from the initial amount of the daughter present in the material.
After an organism has been dead for 60,000 years, so little carbon-14 is left in it that accurate dating becomes impossible.