Naturally occurring iron consists of four stable isotopes: 5.845% of ⁵⁴Fe, 91.754% of ⁵⁶Fe, 2.119% of ⁵⁷Fe and 0.286% of ⁵⁸Fe. There are 24 known radioactive isotopes, the most stable of which are ⁶⁰Fe and ⁵⁵Fe. Wikipedia