Helium dating

Helium Dating (or He dating) is the method of age determination that depends on the production of helium during the decay of the radioactive isotopes uranium-235 (U-235), uranium-238 (U-238), and thorium-232 (Th-232). Because of this decay, the helium content of any mineral or rock capable of retaining helium will increase during the lifetime of that mineral or rock, and the ratio of helium to its radioactive progenitors then becomes a constant. Since radioactivity is a first order decay process, the calculation of the mineral or rock's age is trivial.

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The helium content may be artificially lowered by improper handling of the specimen, as it may leak from the crystal lattice during grinding or other rough mechanical handling.