Isotopes of osmium

Osmium (₇₆Os) has seven naturally occurring isotopes, five of which are stable: Os, Os, Os, Os, and (most abundant) Os. The other natural isotopes, Os and Os, have extremely long half-lives (1.12×10 years and 2.0×10 years, respectively) and for practical purposes can be considered to be stable as well. Os is the daughter of Re (half-life 4.12×10 years) and is most often measured by the Os/Os ratio. This ratio, as well as the Re/Os ratio, have been used extensively in dating terrestrial as well as meteoricrocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons.

There are also 31 artificial radioisotopes, the longest-lived of which are Os with a half-life of 6.0 years, Os with 92.95 days, and Os with 14.99 days; others are under 30 hours, with most under seven minutes. There are also 19 listed nuclear isomers, the longest-lived of which is Os with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.