A kratonite bar is a bar of refined Kratonium ore. It can be created through the Smithing skill by using kratonium ore on a furnace, requiring level 30 Smithing and granting 25.9 Smithing experience. The kratonium ore itself can be mined from the rocks scattered throughout the dungeon, obtained as a monster drop, or bought from the Smuggler.
A kratonite bar can be smithed on an anvil through the Smithing skill to create Kratonite equipment, granting between 37 and 41.5 Smithing experience per bar used. A list of kratonite items that can be smithed from kratonite bars and the Smithing levels required can be found here.
Five kratonite bars are used along with 5 utuku branches to build a cooking range in the hotspot located in the start room of a dungeon.