USGS -- Isotope Tracers -- Resources
Periodic Table--Strontium. The alkali earth metal strontium has four stable, naturally occurring isotopes: 84 Sr (0.56%), 86 Sr (9.86%), 81 Sr (7.0%) and 88 Sr (82.58%). Only 87 Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87 Rb, which has a half-life of 48,800,000 years. Thus, there are two sources of 87 Sr in any material: that formed during
