Board Thread:Suggestions forum/@comment-25012056-20160725221323/@comment-26298013-20160729013041

As far as I know, while there may have been mithril under Meneltarma, it is now inaccessible. Only the very peak of the mountain still protrudes over the waters---and it has only been found by ancient Gondorian seafarers (I think. They might not have found it, however).

So that's technically out (Not for mod purposes, perhaps). The mithril for the gates of Minas Tirith would had to have come from the stocks of mithril in the Lonely Mountain. Erebor must have imported/inherited large quantities of mithril for them to consider making a coat for an elven child (Seriously, why else would you waste that much of the world's most precious metal on something that the owner will outgrow [And never use in battle, which is the entire purpose of armor] in a few years?). The mithril used in the gates of Minas Tirith would MOST LIKELY be used sparingly, as reinforcements at critical points. Perhaps just decoration, in which case only a tiny amount, hammered extremely thin, would be needed. Either way, the White Mountains probably did not have their own supplies of mithril. It may have been based off of titanium, but that does not mean that mithril must share titanium's distribution.