An Adamant pickaxe requires 31 Mining to mine with, and 30 Attack to wield. As pickaxes cannot be smithed, you must buy them from other players or stores. They can be bought from Nurmof the dwarf in the second chamber to the east (Ice Mountain entrance), within the Dwarven Mines.
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Ben_Goten78; Offspringkid; Lord V Unit; Pure Staker; StephenDA18