Gold is the currency used in UnderMine and you will be able to find it on your travels in chests, plants, skulls, statues, crystals, crates, vases, and from gold deposits within the different rooms. Gold deposits can be found inside boulders or gold veins so make sure you get into the habit of checking all of the walls in a room for gold viens before moving on to he next room.
The gold you find in UnderMine can be used to purchase food, relics, and a variety of different items from shops. Gold can also be used to purchase upgrades from the shops back in your base when you die. Remember though that upon death you will lose a portion of the gold you have collected, the amount will depend on your gold integrity; all gold can be kept if you complete a run or pick up the Sewing Kit.