they each stopped losing xenon. This in turn corresponds to a difference in age of closure in the early solar system. The 26Al – 26Mg chronometer Another example of short-lived extinct radionuclide dating is the – chronometer, which can be used to estimate the relative ages of chondrules. decays to with a half-life of 720 000 years. The dating is simply a question of finding the deviation from the natural abundance of (the product of decay) in comparison with the ratio of the stable isotopes /. The excess of (often designated *) is found by comparing the / ratio to that of other Solar System materials. The – chronometer gives an estimate of the time period for formation of primitive meteorites of only a few million years (1.4 million years for Chondrule formation). A terminology issue In a July 2022 paper in the journal Applied Geochemistry, the authors proposed that the terms “parent isotope" and "daughter isotope” be avoided in favor of the more descriptive "precursor isotope" and "product isotope", analogous to “precursor ion” and “product ion” in mass spectrometry. See also Hadean zircon Isotope geochemistry Paleopedological record Radioactivity Radiohalo Sensitive high-resolution ion microprobe (SHRIMP) References Further reading Conservation and restoration of cultural heritage