Once you have reached the mining skill level of 325 or above, the best place on where to mine in WoW for Adamantite would be at Nagrand.
Nagrand belongs to the Burning Crusade zone which is located in Outland that lies just south of Zangarmarsh. Additional landmarks would be Terokkar Forest which is south of Nagrand; southwest of it would be Hellfire Peninsula.
There are a few good caves to mine in Nagrand which is marked on the maps in the mining map below.
The red crosses marked on the map shows the caves that are worth exploring into because of the abundance of Adamantite in them.
- Your mining skill is at least 350
- You have learnt Grand Master Miner to farm effectively
Before moving on to the next zone.