Because Ar has a very short half-life, it is guaranteed to be absent in the sample beforehand, so it's a clean indicator of the potassium content.

potassium argon dating animation-11

A variant of the K-Ar method gives better data by making the overall measurement process simpler.

The key is to put the mineral sample in a neutron beam, which converts potassium-39 into argon-39.

The rock sample to be dated must be chosen very carefully.

Any alteration or fracturing means that the potassium or the argon or both have been disturbed.

With each increment in quality, more subtle sources of error have been found and taken into account.

Because radiometric dating utterly refutes their biblical interpretations, young-Earth creationists (YECs) are desperate to undermine the reliability of these dating methods.

Young rocks have low levels of Ar, so as much as several kilograms may be needed.

Rock samples are recorded, marked, sealed and kept free of contamination and excessive heat on the way to the lab.

These dating methods have been under constant improvement for more than 50 years.