A rune bar is a bar of refined runite ore. It can be created at 85 Smithing skill by smelting 1 runite ore and 8 pieces of coal in a furnace granting 50 experience. Outside of Daemonheim, it is the highest level bar in the game.
At any anvil, players can smith rune bars into various rune weapons and armour, granting 75 Smithing experience per bar used. When smelted and smithed, a rune bar produces 125 Smithing experience in total. A list of items that may be produced from rune bars, the Smithing levels required to produce them, and other information may be found here. Aside from its uses in Smithing, a rune bar is a tertiary ingredient for a rune minotaur pouch. As such, it may be received from a box of summoning ingredients.
Assuming all materials are purchased on the Grand Exchange, the cost to produce a rune bar is 13,439 coins. As a rune bar is currently worth 14,314 coins, each bar represents a profit of 875 coins. Smelting rune bars at the Blast Furnace, which reduces the required number of coal per bar by 50%, reduces the cost per bar to 11,881 coins; the profit/loss for smelting rune bars at the Blast Furnace is 2,433 coins each. Players who use the Superheat Item spell, along with a staff of fire, to smelt rune bars incur a profit/loss of 516 coins.
The best high alchemy return for smithed rune items is obtained from the Rune 2h sword, Rune platelegs and Rune plateskirt, each giving 38,400 coins or 12,800 per bar, and requiring level 99 smithing. A lower level alternative is the Rune sword which gives 12,480 coins from a single bar at level 89.