Stardew Valley created by ConcernedApe.
Images used for educational purposes only.

You’ll trigger this quest on the fifth day of Winter in your second year. When you wake up in the morning you’ll have a letter from the Wizard, asking for an Iridium Bar. 

This is not a simple feat. Iridium Bars are among the more precious items in the game, and are used to upgrade your tools to their highest forms. The Iridium Ores you need to make the Bars are also pretty rare in and of themselves, and you may go entire months without finding enough of the stuff to make an Iridium Bar. Here are some ways to get Iridium Ore:
  • Occasionally you’ll find meteorites in the fields of your farm. (Hopefully they haven’t crushed your crops.) If you take a Golden Pickaxe to one of these meteorites it will drop several Iridium Ores.
  • Some of the lower-level monsters in the Mines, particularly the Void monsters, will drop Iridium Ore. You stand a better chance of getting these Ores from monsters in the Skull Cavern, however.
  • You can mine Iridium Ore from certain stones, like any other Ore. These stones are very rare, however, so don’t rely on this method too much. You’re most likely to find them in the Skull Cavern and the Quarry.
  • Perhaps the most ‘reliable’ source of Iridium Ore is the humble Geode. Omni and Magma Geodes both have a chance to contain Iridium Ore, usually multiple Ores at a time. Magma Ores are best found on the last twenty or so levels of the Mines; Omni Geodes are most plentiful in the Skull Cavern.
Toss your Ores in a Furnace and wait a few in-game hours, or overnight. Your iridium Bar will be done soon enough. Snag it and take it to the Wizard, in his Wizard’s Tower, to the west of Marnie’s Ranch. He’ll give you a whopping 5,000 gold for the delivery, and you'll earn a jump in affection with the weirdo.