A dating method for minerals based on the measurment of the ratio of radioactive potassium to radioactive argon. Radiocative potassium decays to form radioactive argon at a known rate. Argon is rare since it can readily escape to the atmosphere. Thus, its presence in a freshly opened stones is assumed to be due to the decay of potassium. The age of meteorites and volcanic stones are measured by this method.
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
- Encyclopedia Britannica, http://www.britannica.com Comment: "potassium-argon dating." Encyclopædia Britannica. 2004. Encyclopædia Britannica Premium Service. 9 Nov. 2004 .