Iridium

Iridium. Almost Platinum, not quite. 77 protons, 77 electrons, and 115 neutrons. Iridium rivals it's neighbor, Osmium, as the densest elements. It is the rarest non-radioactive, non-noble gas element in the Earth's crust. It is relatively common in meteorites, which has been used as evidence of a large meteor causing the extinction of the dinosaurs. A layer of Iridium was found in a concentration hundreds of times greater than naturally occurs on Earth.

The density of Iridium is probably the reason it doesn't occur often in the Earth's crust. During the formation of the planet, it sank down toward the core. It is found uncombined in nature with platinum and other platinum group metals in river deposits. Naturally occurring iridium alloys include osmiridian and iridiosmium, both of which are mixtures of iridium and osmium. It is recovered commercially as a by-product from nickle mining and processing.

Iridium is the most corrosion-resistant metal known. It's been known to be used for hardening platinum, since it is very brittle, hard, and difficult to work. It has also been used in a powdered form to paint porcelain.

Iridium . . . pretty cool.