Iridium is an extremely rare, dense, silvery-white metal that resists corrosion better than almost any other element. Scientists named it after Iris, the Greek goddess of rainbows, because iridium's chemical compounds can shimmer with brilliant, changing colors.

This metal is so rare that all the iridium ever mined would fit in a small room, yet it plays fascinating roles in science and history. Iridium is twice as dense as lead and can survive conditions that would destroy most other metals. These properties make it valuable for coating spark plugs in aircraft engines and tipping fountain pen nibs, where durability matters most.

Iridium became famous in geology for helping solve one of science's greatest mysteries. In 1980, scientists discovered a thin layer of iridium-rich clay in rocks formed 66 million years ago, right when dinosaurs went extinct. Since iridium is common in asteroids but rare on Earth's surface, this iridium layer provided crucial evidence that a massive asteroid impact caused the dinosaur extinction. The impact threw up clouds of dust containing iridium from the asteroid, which then settled worldwide as a thin layer that we can still detect today. This discovery revolutionized our understanding of mass extinctions and how suddenly Earth's history can change.