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J value uncertainty can be minimized by constraining the geometry of the standard relative to the unknown, both vertically and horizontally.
The NMGRL does this by irradiating samples in machined aluminum disks where standards and unknowns alternate every other position.
Step-heating is the most common way and involves either a furnace or a laser to uniformily heat the sample to evolve argon.
The primary standard must be a mineral that is homogeneous, abundant and easily dated by the K/Ar and Ar methods.
Mechanical crushing is also a technique capable of releasing argon from a single sample in multiple steps.
Laser probes also allow multiple ages to be determined on a single sample aliquot, but do so using accurate and precise spatial control.
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.