You can find several types of gems and Eternium Ore from Burning Crusade specific ore nodes.
You will find various types of green quality gems through mining relatively often. It is possible to mine blue (rare) gems, but this happens very rarely.
Eternium Ore can be found at a ~10% rate from Rich and regular Adamantite and Khorium deposits. It has a ~2% chance to come from Fel Iron Deposits.
In addition, you can find two types of motes through mining. Motes of Earth come from Fel Iron, Adamantite, rich Adamantite and Khorium deposits. Motes of Fire comes only from Fel Iron deposits.