Most of the planetary crust has been long destroyed through the subduction of tectonic plates, the earliest surviving piece previously discovered dating back only 2.7 million years. So the rock that emerged in Hudson Bay is the oldest geological treasure ever uncovered. The scientists were able to trace back the rock’s age by using the latest geological technique, developed only a decade ago and available in just a few geology labs. They searched for a rare isotope called samarium-146, which was only produced on Earth during the planet’s first 500 million years of existence, when the cooling process gave birth to the planetary crust. The study revealed the granite formation to be just one geological step away from Earth’s original crust. The rock aged between 4.2 billion and 4.3 billion years managed to survive the planet’s violent evolutionary process.