Ubatuba magnesium fragments (Brazil, ~1957).

The Ubatuba fragments are pieces of metal said to have come from an exploding aerial object off the Brazilian coast near Ubatuba around 1957, long touted as 'UFO debris' because of claimed unusually pure magnesium. In modern reanalysis Stanford's Garry Nolan reported some subsamples show 'extraordinarily altered' magnesium isotope ratios, while one alleged-magnesium fragment turned out to be near-pure silicon. The samples remain a contested, much-studied test case for materials-based UAP claims. **Replication status:** disputed · Mg terrestrial — Powell et al. 2022 (JSE 36:1): Mg isotopes within terrestrial limits; the 1957 '100% pure' claim was an instrument detection-limit artifact. Decades of non-reproducible inter-lab trace values.