[mhagain]

Originally Posted by Zigûr

Good catch, I'd forgotten about these remarks. Interestingly the first seems to contradict the widely-presented assumption that the Grey Mountains and the Iron Hills were Second and Third Age remnants of the Iron Mountains. This text implies they were separate features as early as the First Age.

It's still possible; if the East-central Iron Mountains were damaged at the Breaking of Utumno and Melkor's first Chaining the Grey Mountains and Iron Hills could be remnants of that part of the Iron Mountains, and therefore the remnants date back a lot further than the Second or Third Ages.