Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
an indirect method of dating fossils, esp. those in very ancient volcanic rock, by using potassic minerals in the same strata as a reference: a natural radioactive isotope of potassium, K-40, decays steadily into argon, which accumulates in the minerals and is measured to determine age
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potassium-argon dating - Science Definition
The American Heritage® Science Dictionary
A method of radiometric dating , involving analysis of the ratio of potassium 40 (a radioactive isotope of potassium) to argon (the product of radioactive decay of potassium 40) in a given sample.
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