Isotopes of iridium

There are two natural isotopes of iridium (₇₇Ir), Ir and Ir, both stable. In addition, there are 40 known radioisotopes with mass numbers 164 through 205, the most stable being Ir with a half-life of 73.82 days, and many nuclear isomers, the most stable of which is Ir with a half-life of 241 years. All other nuclides have half-lives under two weeks, most under a day. All isotopes of iridium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

The isotope Ir was the first one of any element to be shown to present a Mössbauer effect. This renders it useful for Mössbauer spectroscopy for research in physics, chemistry, biochemistry, metallurgy, and mineralogy.