Adamantite ore

Adamanite ore requires mining level 70. They grant 716 experience per rock mined, and you get 2 ores. You can mine adamantite in the Dwarven mines (2 rocks), deep in the Wilderness just south of the Lava maze (4 or more rocks), and on the Fremennik isles.

An Adamantite ore can be smelted into an Adamant bar in a Furnace, using 1 Adamanite ore and 3 Coal. You can also use the spell Superheat to get an Adamant bar, but you still need to have atleast 3 Coal and the required runes for the spell. Using this spell will grant 148 Smithing xp and 692 Magic xp.

Adamant bars are further refined in the Smithing skill. They will grant 430 smithing xp for each bar you use while smithing.