Potassium-Argon Dating Potassium-Argon (K-Ar) dating is the most widely applied technique of radiometric dating. Potassium is a component in many common minerals and can be used to determine the ages of igneous and metamorphic rocks.

## How is potassium used for dating?

Potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.

## Why is potassium-40 useful for radioactive dating?

The very slow decay of potassium 40 into argon are highly useful for dating rocks, such as lava, whose age is between a million and a billion years. The decay of potassium into argon produces a gaseous atom which is trapped at the time of the crystallization of lava.

## Can potassium be radioactive?

Potassium (K) is a widely encountered element with a very small fraction of its atoms, about 0.012%, being radioactive. These K-40 atoms spontaneously decay, releasing electrons (beta radiation) as well as gamma rays.