It costs 2,257 to manufacture one bar using materials bought off the Grand Exchange. One can expect a net gain of 96 each at current market prices. If the player is using Superheat Item, then the cost is 2,969, or 2,681 if a fire staff is used. Using the Blast Furnace to halve the coal required results in a cost of 1,708 and net gain of 645.
Adamant is the heaviest of all ores and this type of bar is heavier than any other bar with the exception of an obsidian bar, which weighs 3 kg.
An adamant bar can be smithed on an anvil through the Smithing skill to create adamant weapons and armour, granting 62.5 Smithing experience per bar used. When an adamant bar is smelted and then forged into an item, the total experience per bar is 100, which is conveniently easy to remember. A list of adamant items that can be smithed from adamant bars and the Smithing levels required can be found here.
The word "adamant(ite)" is abstracted form the Greek word "adamas" (also the root of the word "diamond") meaning "unconquerable," and refers to any strong metal.
For little more than half a year it was the strongest metal in RuneScape Classic, being released in January 2001 while Runite wasn't released until August of the same year.
The name "adamantite bar" was changed to "adamant bar" in November 2010, because adamantite was the name of the ore, not the metal. The name of "Runite bar" was also changed to "Rune bar" for the same reason.