Through time, the number of parents constantly decreases while the number of daughters constantly increases.Theoretically, although the number of parents will become insignificantly small, there should never come a time when all of the parent population has decayed to daughters.
In other instances, a mineral can be created with a substantial amount of a daughter product already incorporated.
For example, K from the Ca that was originally in the sample.
Suppose that at its inception, a sample contains 100 units of a parent radioisotope.
After one half-life has passed, there will remain 50 units of the parent isotope, and 50 units of the daughter product will have been produced.
Results of such studies are most effeective if enough time has passed to let a substantial amount of the daughter product grow (perhaps 10%), and are of limited use if morethan six half-lives have passed (because not enough of the parent material remains to study).
Dating of archaeological samples is commonly conducted using C-14, which has a half-life of 5730 y.
Dating of geologic samples is most often accomplished using K-40 (with a K-Ar half-life of 1.3 x 10 y).
Interpretation of data must take into consideration several factors that can yield inaccurate results.
Beta particles originate in the nucleus, presumably by breakdown of a neutron into its proton-electron components.