Neptunite

Neptunite is a mineral item that can be found in the Magma Geode and the Omni Geode. It can also be dropped by Black Slimes, making it one of the mineral drops that can appear from both geode processing and monster loot.

In addition to being a collectible mineral, Neptunite has a use in tailoring. When placed in the spool of the Sewing Machine with a dyeable clothing item in the feed, it acts as a black dye. This makes it useful for changing the color of clothing through the sewing system.