Such contamination can occur if a sample is exposed to carbon compounds in exhaust gasses produced by.
In addition, any argon that existed prior to the last time the rock was molten will have been driven off by the intense heat.
Radiometric dates, like all measurements in science, are close statistical approximations rather than absolutes.
This will always be true due to the finite limits of measuring equipment.
In a separate article (Radiometric dating), we sketched in some technical detail how these dates are calculated using radiometric dating techniques.
The atoms of crystalline solids, such as pottery and rock, can be altered by this radiation.
Specifically, the electrons of quartz, feldspar, diamond, or calcite crystals can become displaced from their normal positions in atoms and trapped in imperfections in the crystal lattice of the clay molecules.
These energy charged electrons progressively accumulate over time.
When a sample is heated to high temperatures in a laboratory, the trapped electrons are released and return to their normal positions in their atoms.
This causes them to give off their stored energy in the form of light impulses (photons). A similar effect can be brought about by stimulating the sample with infrared light.