five isotopes of zinc are found in nature. 64zn is the most common isotope, with 48.63% of naturally occurring zinc. this isotope has a half-life of 4.3x1018 years. this is so long, that its radioactivity can be ignored. similarly, (0.6%), with a half life of 1.3x1016 years is usually considered to not be radioactive. the other isotopes found in nature are (28%), (4%) and (19%).