Iridium

Iridium is a rare, end game metal added by IndustrialCraft 2, with GregTech adding more functionality to it. With IndustrialCraft only Iridium can only be aquired from UU matter, with GregTech Iridium can also be mined from Iridium ore, or centrifuged from platinum dust. Iridium ore is very rare, with a spawn rate of 1 ore per 5 chunks average. Ingame this will almost always be lower since this ore spawns random from height 1-99, so if the game tries to spawn it above surface, no Iridium Ore appears at all. In a normal biome (height 64) this means an avarage of 1 ore every 10 chunks, and in ocean biomes (level 32), one every 20 chunks.