Mint chunks are a viable resource in the game, and they’re useful to create distinct pieces of armor to wear, along with valuable tools. It’s a resource you want to consider obtaining closer to when you start to get level 2 tools and pieces of equipment, but finding them early is never a bad idea. You do have to wait a bit before you can start to harvest this resource, though.
You can find mint chunks close to where you first encounter the mysterious device when playing the main quest. They’re inside the Ice Caps Mint Container, and you need to hit the top of the container a few times to open it. When it’s unlocked, you should be able to interact with a mint chunk, but you need a level 2 hammer to crack them apart. You can earn this by creating an insect hammer, which requires four stinkbug parts, four berry leather, and one boiling gland. When you have your insect hammer, you can return to the Ice Caps Mint Container to harvest your mint gold.
Take your hard-earned mint back to your camp to have it analyzed at a field station. There, you can learn several useful recipes to make use of the resource. It’s a high quality item, so think about how you want to spend each piece of your precious mint chunk.