Iridium is one of the rarest metals found on Earth. It is usually associated with extraterrestrial impacts, as the element occurs more abundantly in meteorites
https://www.pbs.org/video/day-dinosaurs-died-sytqgj/ 66 million years ago, a seven-mile-wide asteroid collided with Earth, triggering a chain of events that coincide with the end of the dinosaurs. But experts have long debated exactly what happened when the asteroid struck and how the giant beasts met their end. Now, scientists have uncovered compelling new clues about the catastrophe.