Eternium Ore

Eternium Ore is mined from Fel Iron, Adamantite, and Khorium veins found in most regions of Outland. Eternium is used in the production of Felsteel.

Source
Eternium Ore is found uncommonly while mining any of the mineral deposits found in Outland:
 * Fel Iron Deposit
 * Nethercite Deposit
 * Adamantite and Rich Adamantite Deposits (Higher chance from rich deposits)
 * Khorium Vein

Smelting (Mining)
Eternium Ore may not be prospected.
 * Smelt Eternium - requires mining skill 350
 * Enchant Chest - Dodge