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(General Physics) 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 1.28 × 109 years. Measurement of the ratio of these isotopes thus gives the age of the mineral. Compare radiocarbon dating, rubidium-strontium dating
a method for estimating the age of a mineral or rock, based on measurement of the rate of decay of radioactive potassium into argon.