Where is rich iron ore mined from?
The Kingsfell area of the North Downs has great tier 3 ore node density. In Evendim, the Parth Anduil area between Tinnudir and Ost Forod is also node rich, but the mobs are a bit higher level. You'll find plenty of nodes in eastern Lone-lands while leveling there.
Go check Lorebook or lotro-wiki.com
(scroll down until you find Ores)
That page shows locations for all of the resources in-game.
Rich Iron Ore: