No, clearly it is implied in the world at that time.
We know that mithril was also found in Númenor:
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For that metal was found in Númenor. [Author's note.] – In "The Line of Elros" (p.232) Tar-Telemmaitë, the fifteenth Ruler of Númenor, is said to have been called so (i.e. "silver-handed") because of his love of silver, "and he bade his servants to seek ever for mithril." But Gandalf said that mithril was found in Moria "alone in the world" (The Fellowship of the Ring II 4). ~ Unfinished Tales, The Disaster of the Gladden Fields, note #31
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Indeed, a strange thing, though I personally rather believe that Gandalf still said the truth, since Númenor was underwater and Aman had been taken away from the world.