A long time ago, in a galaxy far, far away … Kidding! But seriously, about 50 million years ago a large asteroid made almost entirely of iridium crashed into the earth in the area that is now Mexico’s Yucatan Peninsula, near the town of Chicxulub. The resulting dust cloud shut down photosynthesis and destroyed all life on earth that was larger than about 25 kg (including the dinosaurs), and deposited an iridium bearing clay layer around the globe.
Iridium is not a rare metal, but the ability to use it in a manufacturing type environment is fairly unique. The only products that utilize iridium currently are cellular telephones (Motorola), sunglasses (Oakley), and DENSO spark plugs. The reason that iridium is not more commonly used is that it is difficult to manipulate it in a cost-effective manner.
DENSO has used iridium in the development of their complete line of OE platinum spark plugs and that experience helped them create a patented DENSO iridium alloy, in which the iridium is the primary metal complimented by rhodium in order to increase oxidation wear resistance. DENSO’s Iridium Power spark plugs are simply the best spark plugs you can buy!