I'm afraid you're currently on the wrong landmass.
I also don't think steel or iron can be considered almost like mithril - they are, after all, what it is contrasted to. They're strong, certainly, but mithril is also light - and hard to refine into metallic form.
(The first Gate of Gondolin was of wood, while the last was steel; gold comes between steel and silver, which
could be a very oblique hint at
mellyrn, and therefore Lothlorien... but as I've already discounted Lorien, I feel free to say that isn't the case, and Gondolin is not relevant to the solution.)
hS