Potassium 40 dating accuracy
Traditionally, this primary standard has been a hornblende from the Mc Clure Mountains, Colorado (a.k.a. Once an accurate and precise age is determined for the primary standard, other minerals can be dated relative to it by the Ar technique (e.g. However, while it is often easy to determine the age of the primary standard by the K/Ar method, it is difficult for different dating laboratories to agree on the final age.Likewise, because of heterogeneity problems with the MMhb-1 sample, the K/Ar ages are not always reproducible.
In order for an age to be calculated by the Ar technique, the J parameter must be known.
However, the Argon, a noble gas, constitutes approximately 0.1-5% of the Earth's present day atmosphere.
Because it is present within the atmosphere, every rock and mineral will have some quantity of Argon.
Argon loss occurs when radiogenic K by a fast neutron reaction) can be used as a proxy for potassium.
Therefore, unlike the conventional K/Ar technique, absolute abundances need not be measured.