These steps help remove as much atmospheric Ar from the sample as possible before making the measurement.
Next, the mineral sample is heated to melting in a vacuum furnace, driving out all the gas.
This mineral sample is then baked gently overnight in a vacuum furnace.
The atoms in some chemical elements have different forms, called isotopes.
Potassium-40 on the other hand has a half like of 1.25 billion years and is common in rocks and minerals.
A precise amount of argon-38 is added to the gas as a "spike" to help calibrate the measurement, and the gas sample is collected onto activated charcoal cooled by liquid nitrogen.
Then the gas sample is cleaned of all unwanted gasses such as H, nitrogen and so on until all that remains are the inert gasses, argon among them.
These effects must be corrected, and the process is intricate enough to require computers.