A mineral brought back from the moon by astronauts in 1969 has been found on Earth for the first time, buried in billion-year-old rocks in Australia. Tranquillityite, named after the moon's Sea of Tranquility, had long been considered "the moon's own mineral." Two other previously unknown minerals brought back from the moon were found on Earth in the decade after the Apollo landings.
Tranquillityite mainly consists of iron, silicon, oxygen, zirconium, titanium, and yttrium, reports the Telegraph, and although it has no economic value, scientists say it is very useful for gauging the age of other rocks in which it is embedded. The Australian paleontologist who found it in samples from six sites says the find was "a bit of a thrill" and he's surprised it wasn't found earlier. "I suspect that people weren't really looking that hard," he tells the Sydney Morning Herald. (Read more moon stories.)