The Potassium-Argon dating method is the measurement of the accumulation of Argon in a mineral. It is based on the occurrence of a small fixed amount of the radioisotope 40K in natural potassium that decays to the stable Argon isotope 40Ar with a half-life of about 1,300 million years.

What is the half-life of potassium-40 Argon-40 radioactive isotope?

1.25 billion years RADIOMETRIC TIME SCALEParent IsotopeStable Daughter ProductCurrently Accepted Half-Life ValuesUranium-235Lead-207704 million yearsThorium-232Lead-20814.0 billion yearsRubidium-87Strontium-8748.8 billion yearsPotassium-40Argon-401.25 billion years2 more rows•Jun 13, 2001