Borderlands 3, like its predecessor, has a few different currencies. While most are self-explanatory, Eridium is a little bit more complicated.
The game explains that you can use it to buy things from Crazy Earl and his vending machine, but how exactly you earn it isn’t explained for a while. So to help answer your question before you have to ask it, here’s out explanation of how to earn Eridium in Borderlands 3.
How to get Eridium
The source of Eridium in Borderlands 3 are the small purple crystals littered throughout the environment. But you won’t be able to break them until you’ve opened the game’s first vault. Once you’ve opened the vault by defeating the boss that guards it, you’ll get a new melee weapon that can destroy the crystals.
Once you break them, these crystals will explode into small Eridium fragments that you can pick up to grant you some of Borderlands 3’s late-game currency.