A marmaros bar is a dungeoneering bar of refined Marmaros ore. It can be created through the Smithing skill by using marmaros ore on a furnace, requiring level 20 Smithing and granting 19.6 Smithing experience. The marmaros ore itself can be mined from the rocks scattered throughout the dungeon, obtained as a monster drop, or bought from the Smuggler.
A marmaros bar can be smithed on an anvil through the Smithing skill to create Marmaros equipment, granting between 28 and 32.5 Smithing experience per bar used. A list of marmaros items that can be smithed from marmaros bars and the Smithing levels required can be found here.