The rate of decay (given the symbol λ) is the fraction of the 'parent' atoms that decay in unit time.
Uranium-lead dating techniques have also been applied to other minerals such as calcite/aragonite and other carbonate minerals.
These minerals often produce lower precision ages than igneous and metamorphic minerals traditionally used for age dating, but are more common in the geologic record.
However, use of a single decay scheme (usually Pb) leads to the U-Pb isochron dating method, analogous to the rubidium-strontium dating method.
Finally, ages can also be determined from the U-Pb system by analysis of Pb isotope ratios alone. Clair Cameron Patterson, an American geochemist who pioneered studies of uranium-lead radiometric dating methods, is famous for having used it to obtain one of the earliest accurate estimates of the age of the Earth.
Radioactive dating is a method of dating rocks and minerals using radioactive isotopes.
This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
Some techniques place the sample in a nuclear reactor first to excite the isotopes present, then measure these isotopes using a mass spectrometer (such as in the argon-argon scheme).
Others place mineral grains under a special microscope, firing a laser beam at the grains which ionises the mineral and releases the isotopes.
those that form during chemical reactions without breaking down).