Last I knew (which was before the iridium shard was added), iridium could only be found in dungeon and stronghold chests, not abandoned mine chests.
However, several IC2 addons provide alternate ways of getting iridium:
1. Iridium Mod
2. Advanced Solar Panels (using the Molecular Transformer)
3. GregTech - the rare Platinum mix vein in GT5u/GT5e (which presumably also exists in GT6) includes iridium ore, and there is small iridium ore in The End. Also, if using version 5.09.14 or later of GT5e, you can centrifuge platinum group sludge dust for a chance of tiny piles of iridium dust (this was migrated from IHL, but versions of IHL old enough to still include it are no longer available from the IHL thread)
Ok thanks Gonna check more dungeons I guess. And if it gets too complicate will check those addons