Atum coins

 You will certainly come across Atum Coins during your journey. They can be found in crates and chests from different structures, or can be looted from various mobs.  Of course, maybe you discovered that water does not exist in most Atum biomes. It vanishes from your bucket just like in the nether. To use water, you actually have to be in an Oasis.
 * Those coins represent a money, just like the emerald for the (Vanilla Minecraft) Villager, that you can use to trade with any Sunspeaker.
 * When found, the coins are dirty, and you have to clean them to be able to use them for trading. Cleaning a coin goes the same as cleaning Broachs, Idols, Necklaces, Rings and Scepters ; you have to toss the dirty element into water (flowing or not).
 * Atum Coins are actually named “Gold Coins” in the game, and the dirty variant “Dirty Coins”.