Naturally occurring zinc is composed of the 5 stable isotopes ⁶⁴Zn, ⁶⁶Zn, ⁶⁷Zn, ⁶⁸Zn, and ⁷⁰Zn with ⁶⁴Zn being the most abundant. Twenty-eight radioisotopes have been characterised with the most stable being ⁶⁵Zn with a half-life of 244.26 days,... Wikipedia