A discovery of this blue zircon crystal, making scientists rethink of Earth‘s early geological history, is 4.4 billion years old, the oldest known fragment of our planet. Image © University of Wisconsin
The zircon crystal, measures just 200 by 400 microns, about twice the diameter of a human hair. It was extracted back in in 2001 from a rock in Australia.
Zircon rocks provide the only physical evidence from the earliest phases of Earth’s geological past. The age for a post-magma-ocean zircon confirmed by atom-probe tomography.
The only physical evidence from the earliest phases of Earth’s evolution comes from zircons, ancient mineral grains that can be dated using the U–Th–Pb geochronometer. Oxygen isotope ratios from such zircons have been used to infer when the hydrosphere and conditions habitable to life were established.