https://www.theregister.co.uk/2020/01/14/oldest_matter_on_earth/

Boffins think they have found the oldest known substance on Earth, dust grains that were formed around five to seven billion years ago - before the Solar System had even formed.

“This is one of the most exciting studies I’ve worked on,” said Philipp Heck, lead author of the paper published in the Proceedings of the National Academy of Sciences on Monday and an associate professor of geophysical sciences at the University of Chicago. “These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy.”