I never did find all the ores. I was missing one in the slums and the temple area. In the end I just completed the quest for the Shadow mage to kill all the demons. They are actually highlighted on the map for you. Not sure if you're aware of this but you can actually accept quests from all three mages and complete which one you want. I chose Shadow Mage because his quest was the easiest.
Currently playing Medal of Honor, Arcania : Gothic 4, Medal of Honor Airborne (360). Next games I'm buying - Fallout New Vegas CE, Fable III CE