A technique for determining the age of minerals based on the occurrence in natural potassium of a small fixed amount of radioisotope 40K that decays to the stable argon isotope 40Ar with a half-life of 1.28ÃÂ ÃÂÃÂ 109 years. Measurement of the ratio of these isotopes thus gives the age of the mineral
A method of estimating the age of igneous rocks or of archaeological objects by measuring the amount of argon that has built up through the radioactive decay of potassium.
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