Isotopes for radiometric age dating
Actually, meteorites that formed by melting, e.g., the various types of achondrites, usually give more precise ages.and most refined of the radiometric dating schemes.During the alpha decay steps, the zircon crystal experiences radiation damage, associated with each alpha decay.This damage is most concentrated around the parent isotope (U and Th), expelling the daughter isotope (Pb) from its original position in the zircon lattice.
These ions are accelerated in an electric field through collimating slits and subject to a magnetic field which causes the ions to follow a curved path. By adjustment of the strength of the magnetic field and suitable placement of an ion collector, the different isotopes can be measured with precision.
Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings. When a given quantity of an isotope is created (in a supernovae, for example), after the half-life has expired, 50% of the parent isotope will have decomposed into daughter isotopes.
After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.
Only the latter two "extinct" nuclides are used in dating.
The use of 14C in meteorite dating is solely based on its production by cosmic rays (and for terrestrial samples, with its production in the atmosphere).