Iridium Ore is an extremely rare ore added by GregTech that is found in single block veins. Iridium Ore can be found in the Twilight Forest and Mystcraft Ages as well as in the Overworld, and can spawn at any level.
Iridium Ore block will yield one Iridium Ore if mined with a Diamond Pickaxe. If silk touch is used, including the silk touch on the Rock Cutter, Iridium Ore may be processed in a Macerator, Rock Crusher, Industrial Grinder or Pulverizer to yield two Iridium Ore items, doubling the output. Due to the scarcity of Iridium this should always be done, especially as a Rock Cutter is a relatively cheap source of Silk Touch. Iridium Ore may be processed in a Compressor (NOT smelted) to get an Iridium Ingot. Fortune does work on this ore, but not well; a test run with Fortune III got 24 ore from 15 blocks.