You may probably wonder how archaeologists determine the age of ancient artifacts or how long a piece of rock exists above the surface. Isotopic dating can tell the age covering hundreds of thousands of years. For instance, common carbon isotope 14C dating can determine the age of artifacts up to 50,000 years. Theoretically, the cosmogenic isotope 41Ca, with a half-life of 99,000 years (17 times that of 14C), can cover an age scale beyond the reach of 14C. Nevertheless, the distribution of 41Ca natural abundances spans the range of 10-15 to 10-16, below the limitation of the present accelerator mass spectrometry (AMS) method.
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Source: Phys.org