Cosmic-ray muon-induced 129I in tellurium ores

1.7 × 10⁷yr-lived ¹²⁹I has been positively detected in two natural tellurium ores by activation analysis with the help of low-level sum-coincidence gamma-ray spectrometry. The observed ¹²⁹I concentrations can be explained as induced by muon reactions on ¹³⁰Te. The detection of ¹²⁹I provides for the first time conclusive evidence for the occurrence of natural long-lived muon-induced nuclides. Most of the ¹²⁹Xe and ¹³¹Xe anomalies observed in natural tellurides are best interpreted in terms of reactions induced by muons and their secondary neutrons.