This is approximately 2,500 times as much Ar as is found in natural muscovite.Thus under certain conditions Ar can be incorporated into minerals which are supposed to exclude Ar when they crystallize.
In electron capture, an electron from the innermost electron shell "falls" into the nucleus, causing a proton to convert into a neutron.
It is not about the theory behind radiometric dating methods, it is about their , and it therefore assumes the reader has some familiarity with the technique already (refer to "Other Sources" for more information).
Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the arbitrary date of 10,000 years.
Potassium argon (40K-40Ar) dating is a form of radiometric dating widely used because of the range of dates for which it is useful.
The technique can be used for dates ranging from earth's beginning, 4550 mya (4.55bn in US terminology) to about 100,000 years ago.
The most widely known form of radiometric dating is carbon-14 dating.